When executing the Redmine test suite, I stumbled upon the following incompatibility. When storing a float value, it is load with a different precision, than it was stored. It occurs in Redmine's sources in test/functional/timelog_controller_test.rb:92
I have extracted the bug into a simple test case for activerecord-jdbc-adapter. The test passes in MRI and fails using JRuby. It may be found attached or on GitHub.