On multiple boss stages i have been stuck unable to use mobility skills or walk but can use other attack skills after using either shift or synchronized strike, i am guessing potentially can happen with any dash/mobility skill.
The most recent occurence was on the 2nd Boss stage of Dragons’ Grotto used synchronized strike into the top right most cluster of dragon eggs and was stuck in the blue slime.
As far as I can tell there is no ‘unstuck’ feature, this could be a solution to all of these pretty persistent issues, I have also had it when the boss dies and you cannt collect loot even at your feet. You need to quit out and reload forcing to lose loot and reclear the stage even if you have technically finished it.