Firstly, let me preface this by saying that I'm a student, not a professional.
I've been using KiCad for a few years, got an academic licence to learn Altium version 19. I've made a couple of minor projects in it -still a beginner, but approaching familiarity.
Upgraded to version 20 last week - boy howdy.
Crashes when you look at it sideways (one seems to be related to docking manufacturer search to the left of the screen?), autorouter shorted out a whole bunch of nets (?!?), but all fixable with a restart or undo.
Until last night it decided whilst I was changing the board layout that my entire ground net was not required. All pads on the net were either now unconnected or in the +5v net. The gnd net was not in the netlist, and DRC didn't see anything untoward, despite the little grounds all over my schematics. Could not undo because I'd saved the file (at a guess), so used dropbox rewind.
TLDR buggy as, not labelled as a beta, what the hell guys!
*Edit to add* - The disappeared ground net was likely due to me shorting out 5v to ground in a schematic. Would have thought that this was worthy of an error to be honest.