I’ve tried that, even cleaned tmp and cache to no avail. Maybe you have to do some more steps in Karaf, not sure.
Then I was struck with [Solved] OH2.5.12 Error downloading mvn:org.openhab.ui.bundles/org.openhab.ui.paper/[2.5.0,2.6)
I dont want to touch the setup any more - its working now.