WASD controls just stop working

I’m building a very simple first person shooter level trying to utilize things I’ve learned from the many tutorials I’ve completed so far. My WASD movement works fine…at first. Every time I play the level, after a couple minutes the WASD controls simply stop working and I can’t move around. The mouse controls still work fine. I’ve used these control setups (which I’ll share below) many times without a problem. I can’t figure out why this is happening here. What could it be?