I've been having this issue too. What seems to be working for me is uninstalling battleye by running the batch file in cmd. The next thing i also did what right click on the destiny 2 .exe and went into the "Compatability" menu. In there I disabled the "fullscreen optimizations", click ok. Then restarted my pc. I also found that it could also be the clock speed with ram, try disabling xmp as well. Hope this helps.