This just happened to me but it was specific to casting a card RIGHT as the main phase was timing out completely. I commented with more detail on a more specific bug here: https://feedback.wizards.com/forums/918667-mtg-arena-bugs-product-suggestions/suggestions/48394052-card-unplayable-timeout

I've gotten the same issue when mutating under very specific conditions, steps to reproduce:

1. 4/4 creature perpetually had -3/-3
2. mutate onto it w/ 3/3 creature
3. put 3/3 creature on top
4. creature dies instantly
5. mutate effects still play out (ontop of played card)
6. played card stays in the stack

Just happened in a quick draft I did

Same here

I wanted to cast Feed the cauldron during my 1st main phase and the timer goes to zero so it passed to the declare attack phase. Feed the cauldron was then out of my hand and not casted. It was floating around for the rest of the game causing me not to see the whole battlefield. Also I almost lost the game because I was one card down. Poor game experience...All is ont the secreenshot. The bug was around 00:15 pm UTC.

I had to concede the match. During the 2nd try the match was also bugged - however, i was able to win the game as the creature that was usable was strong enough to survive/deal dmg while the other create remained unplayable beneath some cards my opponent played.
FYI it was the thrid boss playing blue.

Tutorial got bugged. Cards that were played did not go into graveyard but remained in the air/over the battlefield. At some point i could not select cards that i played before because they were "under" other cards.

Hello,

For this issue, please submit at: https://mtgarena-support.wizards.com/hc/en-us/requests/new and select 'Report a Problem in your Event'.

Thanks!

phantom cards still showing and the animation got stuck, it doesnt allow me to finish the game

Cards dont go to the play mat, hard to play when you can't see anything

During merfolk tutorial mission, cards stopped playing and simply levitated in the air. Attached is a log report. Please look into this, as new players shouldn't be confronted with game breaking bugs this early on, thank you.

I cast a drakuseth and it resolved and stayed on the stack and broke the counters in the game

Hello,

For this issue, please submit at: https://mtgarena-support.wizards.com/hc/en-us/requests/new and select 'Report a Problem in your Event'.

Thanks!

Cards don't disappear after being played.

They block the view of other cards.

Cards remain "Displayed" after being played from their owner's hands... indefinitely.

Cards are sticking to the screen on the side and in the middle of the field and not going away after being played. Also not being displayed properly on the battlefield as well.

The Vendillion Clique had been on the stack for the majority of the game after I had attempted to cast it. Its failure to resolve cost me the match.

A spell was stuck on the stack for the remainder of the game after I tried to cast it. Losing the card cost me the match.

Hello,

For this issue, please submit at: https://mtgarena-support.wizards.com/hc/en-us/requests/new and select 'Report a Problem in your Event'.

Thanks!

I play a card and the card image remains in the stack area and does not appear on the battlefield or graveyard. At the same time, the images of permanents on the battlefield "freeze" too. Lands do tap for mana, creatures do attack and die. But I dont see these changes. I cast a planeswalker, his image is in the stack area overlayed by other images already stuck there. If i click on the planeswalker image on the stack, I get to activate its abilities...
Playing on a PC with Win 7.
This issue happend from time to time in a small scale before the 18.7.2023 update, but right after the update it happened ca. every second game and lasted for several turns until I lost, because I could not use my cards, or until it suddenly fixed itself.