Customize page freezes and glitches

For about a week now, my Customize page (under Appearance) has been freezing and glitching. The page is very slow to move or click anything and the preview of the screen on the right randomly blinks. Its very frustrating as it is hard to edit my page. So far I’ve tried it on different computers, web browsers, temporarily changed the theme, and removed a Meta Slider widget I had on there….but it is still doing it! I couldn’t find anyone online who seemed to have this exact issue. Would there be something else that is making it do this? I just started building my site a month ago and don’t think I have a whole lot of content on there that would make it slow down like that. Help please! Thank you!