When a player is disconnected during gameplay, and often leads to being dropped from their event.

When lag causes a misclick or skipped action. The user isn't disconnected from the client though.

Have Vine Gecko and four lands on the battlefield (3 Forests, 1 Island).
Try to cast Inscription of Abundace with kicker as the first spell of your turn.
After choosing modes, the game asks to pay 3GG, thought it should be reduced to 2GG with the Gecko.

When the User Experience or User Interface is involved in an issue. Generally not a technical bug, but where the client could be improved to help reduce confusion.

I was playing and Magic Online suddenly crashed and I pressed the buttons in an attempt to get back. It turns out that the game recorded what I pressed and still crashed. When I came back to the game, after reopening Magic Online, he understood that I "pressed" the buttons even with him frozen and that cost me the game.

Raka Santuary does not recognize when you control a blue permanent and a white permanent.

I cast a manamorphose for double red, cast the second pay it with the 2 manas of the first manamorphose and automatically add other 2 red mana without the possibility to choose the color (I would add red and black)

I cast the new spell shatterskull pass and it automatically set X = 1.

Ceta Sanctuary does not recognize second state

quando estava faltando no meu relógio 14:20 o oponente usou a carta Cast Down que não pode ser usada.

Party calculation doesn't work properly, as seen in the screenshot attached

When I cast Crux of Fate to kill all creatures Kalitas exiled the Birds of Paradise I owned that they controlled, when Kalitas specifies it only triggers on creatures of my controlling dying. The Zombie Token resulting from this trigger was then able to attack and kill a planeswalker next turn when that zombie shouldn't have been in play

When Volrath's Shapeshifter takes on a new shape due to the top card in the graveyard being a creature card, it becomes invisible and cannot be used to attack, block or otherwise interact with.

As can be see in the attached chatlog, the etb ability of the creature in the graveyard still triggered (that creatures being Vendilion Clique).

I activated a Volrath's Shapeshifter and went to click the Hellkite Overlord in my hand. The game stalled, and rebuilt twice before stopping at Turn 1 with our original hands. At that point, the game forced us to yield about five turns each, including discarding to hand size.

Confounding conundrum recognizes the first land entering the battlefield as a result of field of ruin as if it was the second land, forcing you to return 1 land to your hand.

During a Double Masters Sealed League I activated the -14 ability of Karn Liberated. This did not end well. First the entire game up to that point was auto-replayed twice, taking several minutes. Then, a new game was started, with none of the permanents exiled by Karn in play, and both players' timers reset to 25:00. Our stops also didn't work, and priority auto-passed for me and my opponent to our cleanup steps for the first 20-30 turns of the game (before eventually working again).