`sort!': comparison of Array with Array failed (ArgumentError)

[wemasoe]

Hello,

i appreciate the concept of this theme, but i get an error i am not able to solve.
i am using the docker compose file from the project.

server_1  | ruby 2.7.1p83 (2020-03-31 revision a0c7c23c9c) [x86_64-linux-musl]
server_1  | Configuration file: /src/_config.yml
server_1  |             Source: /src
server_1  |        Destination: /src/_site
server_1  |  Incremental build: disabled. Enable with --incremental
server_1  |       Generating...
server_1  |    GitHub Metadata: No GitHub API authentication could be found. Some fields may be missing or have incorrect data.
server_1  |   Liquid Exception: Liquid error (/src/_includes/custom/getting_started_series.html line 5): comparison of Array with Array failed included in pages/mydoc/mydoc_build_scripts.md
server_1  | /usr/gem/gems/jekyll-3.9.0/lib/jekyll/filters.rb:304:in `sort!': Liquid error (/src/_includes/custom/getting_started_series.html line 5): comparison of Array with Array failed included  (Liquid::ArgumentError)


...

server_1  |     from /usr/gem/gems/jekyll-3.9.0/exe/jekyll:15:in `<top (required)>'
server_1  |     from /usr/local/bundle/bin/jekyll:29:in `load'
server_1  |     from /usr/local/bundle/bin/jekyll:29:in `<main>'
server_1  | /usr/gem/gems/jekyll-3.9.0/lib/jekyll/filters.rb:304:in `sort!': comparison of Array with Array failed (ArgumentError)

...

server_1  | jekyll 3.9.0 | Error:  Liquid error (/src/_includes/custom/getting_started_series.html line 5): comparison of Array with Array failed included
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/filters.rb:304:in `sort_input'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/filters.rb:243:in `sort'
server_1  |     from /usr/gem/gems/liquid-4.0.3/lib/liquid/strainer.rb:56:in `invoke'
server_1  |     from /usr/gem/gems/liquid-4.0.3/lib/liquid/context.rb:86:in `invoke'
server_1  |     from /usr/gem/gems/liquid-4.0.3/lib/liquid/variable.rb:84:in `block in render'
server_1  |     from /usr/gem/gems/liquid-4.0.3/lib/liquid/variable.rb:82:in `each'
server_1  |     from /usr/gem/gems/liquid-4.0.3/lib/liquid/variable.rb:82:in `inject'
server_1  |     from /usr/gem/gems/liquid-4.0.3/lib/liquid/variable.rb:82:in `render'
server_1  |     from /usr/gem/gems/liquid-4.0.3/lib/liquid/tags/assign.rb:26:in `render'
server_1  |     from /usr/gem/gems/liquid-4.0.3/lib/liquid/block_body.rb:103:in `render_node_to_output'
server_1  |     from /usr/gem/gems/liquid-4.0.3/lib/liquid/block_body.rb:91:in `render'
server_1  |     from /usr/gem/gems/liquid-4.0.3/lib/liquid/template.rb:208:in `block in render'
server_1  |     from /usr/gem/gems/liquid-4.0.3/lib/liquid/template.rb:242:in `with_profiling'
server_1  |     from /usr/gem/gems/liquid-4.0.3/lib/liquid/template.rb:207:in `render'
server_1  |     from /usr/gem/gems/liquid-4.0.3/lib/liquid/template.rb:220:in `render!'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/liquid_renderer/file.rb:30:in `block (2 levels) in render!'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/liquid_renderer/file.rb:42:in `measure_bytes'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/liquid_renderer/file.rb:29:in `block in render!'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/liquid_renderer/file.rb:49:in `measure_time'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/liquid_renderer/file.rb:28:in `render!'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/tags/include.rb:140:in `block in render'
server_1  |     from /usr/gem/gems/liquid-4.0.3/lib/liquid/context.rb:123:in `stack'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/tags/include.rb:137:in `render'
server_1  |     from /usr/gem/gems/liquid-4.0.3/lib/liquid/block_body.rb:103:in `render_node_to_output'
server_1  |     from /usr/gem/gems/liquid-4.0.3/lib/liquid/block_body.rb:91:in `render'
server_1  |     from /usr/gem/gems/liquid-4.0.3/lib/liquid/template.rb:208:in `block in render'
server_1  |     from /usr/gem/gems/liquid-4.0.3/lib/liquid/template.rb:242:in `with_profiling'
server_1  |     from /usr/gem/gems/liquid-4.0.3/lib/liquid/template.rb:207:in `render'
server_1  |     from /usr/gem/gems/liquid-4.0.3/lib/liquid/template.rb:220:in `render!'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/liquid_renderer/file.rb:30:in `block (2 levels) in render!'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/liquid_renderer/file.rb:42:in `measure_bytes'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/liquid_renderer/file.rb:29:in `block in render!'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/liquid_renderer/file.rb:49:in `measure_time'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/liquid_renderer/file.rb:28:in `render!'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/renderer.rb:126:in `render_liquid'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/renderer.rb:79:in `render_document'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/renderer.rb:62:in `run'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/site.rb:479:in `render_regenerated'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/site.rb:472:in `block in render_pages'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/site.rb:471:in `each'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/site.rb:471:in `render_pages'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/site.rb:192:in `render'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/site.rb:71:in `process'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/command.rb:28:in `process_site'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/commands/build.rb:65:in `build'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/commands/build.rb:36:in `process'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/commands/serve.rb:93:in `block in start'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/commands/serve.rb:93:in `each'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/commands/serve.rb:93:in `start'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/lib/jekyll/commands/serve.rb:75:in `block (2 levels) in init_with_program'
server_1  |     from /usr/gem/gems/mercenary-0.3.6/lib/mercenary/command.rb:220:in `block in execute'
server_1  |     from /usr/gem/gems/mercenary-0.3.6/lib/mercenary/command.rb:220:in `each'
server_1  |     from /usr/gem/gems/mercenary-0.3.6/lib/mercenary/command.rb:220:in `execute'
server_1  |     from /usr/gem/gems/mercenary-0.3.6/lib/mercenary/program.rb:42:in `go'
server_1  |     from /usr/gem/gems/mercenary-0.3.6/lib/mercenary.rb:19:in `program'
server_1  |     from /usr/gem/gems/jekyll-3.9.0/exe/jekyll:15:in `<top (required)>'
server_1  |     from /usr/local/bundle/bin/jekyll:29:in `load'
server_1  |     from /usr/local/bundle/bin/jekyll:29:in `<main>'
documentation-theme-jekyll_server_1 exited with code 1

Thanks for any help and hints.