I had this issue too, basically through the process of elimination I narrowed it down to my character class, and from there found out it was caused by setting morph target values many times every frame. Never had an issue with it before until 4.22, but I fixed it by buffering out the timing using a delay.
No idea what it may be for you but, you can use profilegpuhitches command to record when the hitches happen in the editor and when you stop playing you can see in the profiler what is costing the most time. I tried this myself and it pointed to hzb(mip=1) 512x256 or something and it didnt really help me out, but it might for you.