Does it still happen whenever you close the program and reopen it? That is pretty weird… and have you also tried to restart the computer as well? Usually if I have an application glitching out or lagging like that, a restart will help.
If that does not help, try opening a New Project. Then select File > Import > Select Your Premiere Pro Project that was giving you that glitch issue.
Let me know if any improvements have been made for this. Best of luck!