When using the groovy plugin and providing both classpath and properties settings the plugin produces a command line with the arguments in incorrect order. The classpath is not put as the first argument. I also noticed the order of the arguments is shuffled compared to how entered.
Reverted to groovy-plugin 1.14 (previously used and known to be working) and correct behaviour was restored. We haven't tried to test intermediate versions to try and identify the exact version the behaviour changed in.
In the source changes for the plugin I saw a change for
JENKINS-27964 made in version 1.25 that modified the code that is responsible for building the command. Not sure if this is relevant or significant.