Weird issue, lately.
When I hold down the forward key to move, after a distance my first-person character stops for no apparent reason. When I release the key and press down again, it starts again, and then after a while, stops.
I thought I messed up rigid-body settings, so I used Tin Pot, and same thing. The environment uses mesh colliders. Although I tried it with collision cubes and got the same result.
Comments
Try it with Tin Pot in Direct Control, so we know for sure that it's First Person that's causing it. If it occurs in Direct Control, is there some kind of blocking cutscene/trigger firing?