If you pick a card in your hand before getting a card drawn for your turn while having a start of turn trigger, the newly drawn card is not able to be selected

[Patashu]

~This is possible only in the Tavern Brawl which includes Gearmaster Mechazod.~ You pick a minion in your hand on your opponent's turn and move it across your hand (tested with hand size 4 or lower). After you draw a card for your turn, you won't be able to select it. Your hand will be fixed after you play another card or after Gearmaster Mechazod plays another spell. Canceling a targeted battlecry is another way to fix it.

• https://www.reddit.com/r/hearthstone/comments/412lwv/a_possible_bug_about_hovering_over_cards_while/
• https://www.youtube.com/watch?v=sD6vhN-Aqjg

edit: See note below, not just possible in Tavern Brawl. -Trogg

[culinko]

Reproduced in 5.0.

[PattuX]

Can also happen outside of brawl:

• https://youtu.be/4yZKeNQYNYY

[troggnostupidhs]

I can't reproduce this against the Innkeeper, but I'm not sure if I am doing it correctly.