Redmine

After having installed redmine-5.1.3 onto my Debian 11 server, I encountered the problem that saving an issue results in error. Since I read that Ruby 2.7 is no longer supported, I decided to update to 3.1.6. using ruby-build en renv. Below, a quick switch between versions with server start respond is documented.

Correct server start in Ruby 2.7.4:

redmine@debian-rjm:~/redmine-5.1.3$ bundle exec rails server -e production
=> Booting WEBrick
=> Rails 6.1.7.8 application starting in production http://0.0.0.0:3000
=> Run `bin/rails server --help` for more startup options
[2024-06-19 10:24:58] INFO  WEBrick 1.6.1
[2024-06-19 10:24:58] INFO  ruby 2.7.4 (2021-07-07) [x86_64-linux-gnu]
[2024-06-19 10:24:58] INFO  WEBrick::HTTPServer#start: pid=356143 port=3000
^C[2024-06-19 10:25:14] INFO  going to shutdown ...
[2024-06-19 10:25:14] INFO  WEBrick::HTTPServer#start done.
Exiting
redmine@debian-rjm:~/redmine-5.1.3$ rails --version
Rails 6.1.7.8

Result after switching to 3.1.6:

redmine@debian-rjm:~/redmine-5.1.3$ rbenv local 3.1.6
redmine@debian-rjm:~/redmine-5.1.3$ bundle install
Fetching gem metadata from https://rubygems.org/.........
Resolving dependencies...
Bundle complete! 42 Gemfile dependencies, 75 gems now installed.
Gems in the groups 'development' and 'test' were not installed.
Use `bundle info [gemname]` to see where a bundled gem is installed.
redmine@debian-rjm:~/redmine-5.1.3$ rails --version
Rails 6.1.7.8
redmine@debian-rjm:~/redmine-5.1.3$ bundle exec rails server -e production
Could not find server "". 
Run `bin/rails server --help` for more options.

I'm wondering about empty server name here.
Any hints regarding how to locate the problem?