I don't know why both of them only started now, in Act2, and not since the beginning of the game.

The first one : I am now in the dungeon below the arena and there are quite a lot of locked doors in here so I often use the Shatter spell. But for some reason, most of the time when I cast the spell, the cursor reverts back to the "move there"-hand and nothing happens, no spell. I have to move the cursor over the door and try again, and again, and again...

The other one started a few hours prior, again in an underground dungeon but I don't remember which one. Sometimes when I'm close to a wall and I click to move somewhere else or to grab something, the character gets stuck for a few seconds, unable to do anything. Needless to say the enemies find this situation pretty convenient.

Has anybody else experienced this ?

the first one happens only with grating door. you have to point exactly the door, not the ground behind it.
sticking in the walls i had too. don't know how to evade it.

Happen to me all the time. I learnt to keep myself a tile away from the walls/corners when planning an ambush.