My timeouts got used into an automatic concede while in opponents turn
If the opponent has an incredible long combo (in my case over 500 animation steps), his timeoutes are used because the animations took so long. After his timeouts ran out MY timeouts got used (we both couldn't do anything because of so many animations) and after it finished, I conceded automatically without doing anything.
Yes, I would have lost anyways and we played it like this intentionally, but this shouldn't happen anyways, right? :D

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Evil Broccoli#94549 commented
I was against an opponents who had a loaaad of triggered capabilities. They used all there timeout but the capabilities were still triggering automatically. They could'nt do anything (the markers where put on the first creature by default). But during this time, and while i could do nothing since it wasn't my turn, all my timeout where used and I lost because of that. It was written "opponent turn" on the interaction pannel (where you click resolve and all) so I definitly donc think my timeout should had been used. Thanks !
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kenderx#22628 commented
Same happened to me, I still had outs to draw and a blood token to ***** for an extra draw. Though it was likely I would lose eventually the game was not over.
The game auto-conceded at my next upkeep without giving me a chance to act. Even turning on "Full Control" during my opponent's combo'ing off did not give me an opportunity to act