Colress's experiment & Sky seal stone bugs
So I just encountered a bug, where I couldn't select the second Card in a Colress's experiment (specifically a scoop up net) It wouldn't move no matter how many times I clicked on it or tried to drag it down. This is a pretty game breaking bug, as it denied me a knockout with Galarian Zigzagoon, and I honestly don't see, how something like that could even happen.
Also: Sky seal stone sometimes just doesn't activate. I had 2 games where I used it with a drapion V attacking into mew Vmax and Shadowrider Calyrex Vmax respectively, where I clicked the Vstar Power, it greyed out, the animation played and everything, but still only got 3 prize cards. I presume this is because the server is working too slowly or in some way the client/sever side confirmations are screwed up, but regardless of how it happened, that's just a really bad bug.
These are just the two most game braking bugs I encountered in ca. 1h of play just now, not to mention the plentiful visual bugs like pokemon entrance animations (for the types) just continuing to play on pc until another pokemon switches in, significantly tanking performance (especially the dark one) or how the sound effect from cross switcher plays even If you mute all in game sound. (which is just such an astounding bug that speaks to extreme spaghetti code, which is very worrying this early in development.)