It's possible for the server to send a client's character a movement correction with the wrong movement mode.
This can occur if a project has client adjustment throttling settings enabled:
The adjustment is temporarily delayed. By the time it's OK to send the adjustment, more moves have been processed and the character is now in a different mode. The corrected mode is overwritten by the current mode.
Reported by a licensee:
I've verified this can occur sometimes in the Lyra project, by thrashing movement input while falling onto the ground.
I was only able to tell that this was occurring sometimes with conditional breakpoints, in Lyra using Average/Bad network emulation and thrashing the controller direction while falling onto the ground.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-201287 in the post.