Try this one trick to remove seg faults

Using Sassc and Sprockets seems somewhat prone to segmentation faults
which seems to be a common issue with Sprockets 4. As per
rails/sprockets#633 and
sass/sassc-ruby#207, switching concurrent
asset generation seems to resolve the problem. The unproven theory is
that this reflects that Sprockets 4 uses threads which causes problems
for sassc.

A consequence of this is that asset pre-compilation may be slower than
it could be.

config/initializers/assets.rb

@@ -15,3 +15,10 @@
   #{__dir__}/../../node_modules/govuk-frontend/
   #{__dir__}/../../node_modules/
 ]
+
+# We've experienced segmentation faults when pre-compiling assets with libsass.
+# Disabling Sprockets 4's export_concurrent setting seems to resolve the issues
+# see: https://github.com/rails/sprockets/issues/633
+Rails.application.config.assets.configure do |env|
+  env.export_concurrent = false
+end