Hi Stef, I'm able to reproduce your problems, by not cleaning the packagecache. The new version of Grease-Pharo20-Core is pmm.1. Having a packagecache that contains versions that seem to be newer creates loading of wrong versions. In my case, it tried loading Grease-Pharo20-Core-pmm.17.mcz.
Sharing a packagecache between stable and development branches currently seems to be a bad idea. Cheers, Diego & Stephan
