This is something I have been dealing with for years and have never seen anyone mention it before. I'm not even sure if it's a bug or a "feature". Because of how I use JKL and "Shift i" to go to the in point, I constantly have my timeline get stuck where it will only play one frame at a time with JKL.
Hold down “K” then hold down “shift”. Then let go off “K” and tap “i” then let go of shift. Premiere is now stuck in single frame mode until you hit “K” and “L”.
Am I crazy? Is this susposed to be like that? I get stuck in it like 20 times a day.