Remember my last post about Domino Designer just randomly removing JAR resources from the NSF? I first thought it was something with the ODP and Git but I was wrong.
It turned out that you don't even have to work with an ODP or even Git to run into this problem. The real cause of this is still unclear, I add this to the various hiccups of Domino Designer that we all got used to.
The solution
If you ever experience this, then just check the following: open your NSF in the package manager view. Right mouse click on the project and navigate to "Java Build Path". Under "Source Folders", check if you also have such an entry for the JAR that is removed everytime you select "Project, Clean".
Notice the other 2 entries for the JAR and just remove the one marked here.
Thanks to HCL Support and Paul Albright for sorting this out for me!