Warning: "anyfontsize.sty:3: Invalid UTF-8 byte or sequence at line 3 replaced by U+FFFD"

[VJMReichenbach]

Everytime I compile my main.tex file with tectonic I get the warnings listed below.
My line 3 just defines the documentclass:

\documentclass[
	ngerman,
	accentcolor=1c,
	type=intern,
	marginpar=false
	]{tudapub}

These errors are just a cosmetic thing and the .pdf file builds without any issues. But I want to get rid of the regardless.
I found this issue which lists similar warnings, but the proposed fix:

\XeTeXdefaultencoding "Latin1"
\usepackage[printonlyused]{acronym}
\XeTeXdefaultencoding "UTF8"

doesn't work for me.

Is this an issue with the template my university provides? Did I configure something wrong? Can I do something to fix this?

The described warnings look like this:

note: "version 2" Tectonic command-line interface activated
Running TeX ...
warning: anyfontsize.sty:3:
Invalid UTF-8 byte or sequence at line 3 replaced by U+FFFD.
warning: anyfontsize.sty:3: Invalid UTF-8 byte or sequence at line 3 replaced by U+FFFD.
Running BibTeX on main.aux ...
note: warnings were issued by BibTeX; use --print and/or --keep-logs for details.
Rerunning TeX because bibtex was run ...
warning: anyfontsize.sty:3:
Invalid UTF-8 byte or sequence at line 3 replaced by U+FFFD.
warning: anyfontsize.sty:3: Invalid UTF-8 byte or sequence at line 3 replaced by U+FFFD.
warning: internal consistency problem when checking if main.bbl changed
Rerunning TeX because "main.bbl" changed ...
warning: anyfontsize.sty:3:
Invalid UTF-8 byte or sequence at line 3 replaced by U+FFFD.
warning: anyfontsize.sty:3: Invalid UTF-8 byte or sequence at line 3 replaced by U+FFFD.
warning: internal consistency problem when checking if main.bbl changed
Rerunning TeX because "main.bbl" changed ...
warning: anyfontsize.sty:3:
Invalid UTF-8 byte or sequence at line 3 replaced by U+FFFD.
warning: anyfontsize.sty:3: Invalid UTF-8 byte or sequence at line 3 replaced by U+FFFD.
warning: internal consistency problem when checking if main.bbl changed
Rerunning TeX because "main.bbl" changed ...
warning: anyfontsize.sty:3:
Invalid UTF-8 byte or sequence at line 3 replaced by U+FFFD.
warning: anyfontsize.sty:3: Invalid UTF-8 byte or sequence at line 3 replaced by U+FFFD.
warning: internal consistency problem when checking if main.bbl changed
Rerunning TeX because "main.bbl" changed ...
warning: anyfontsize.sty:3:
Invalid UTF-8 byte or sequence at line 3 replaced by U+FFFD.
warning: anyfontsize.sty:3: Invalid UTF-8 byte or sequence at line 3 replaced by U+FFFD.
warning: internal consistency problem when checking if main.bbl changed
Rerunning TeX because "main.bbl" changed ...
warning: anyfontsize.sty:3:
Invalid UTF-8 byte or sequence at line 3 replaced by U+FFFD.
warning: anyfontsize.sty:3: Invalid UTF-8 byte or sequence at line 3 replaced by U+FFFD.
warning: internal consistency problem when checking if main.bbl changed
warning: TeX rerun seems needed, but stopping at 6 passes
warning: warnings were issued by the TeX engine; use --print and/or --keep-logs for details.
Running xdvipdfmx ...
Writing `main.pdf` (2.08 MiB)
Skipped writing 4 intermediate files (use --keep-intermediates to keep them)