Hello,
1) I have logged in to your Dashboard and don’t see any issue with the page editor http://prntscr.com/sp1wn0
2) Also, don’t see any problem with the Customizer https://gyazo.com/1a9f8d6150d77e05d804d10c42697eba
3) Product categories images were missing, so I just re-added them via Products > Categories > edit the category and upload thumbnails.
4) If I change the size of the image I see the changes https://gyazo.com/7aebd959fb2308d8e03ad5ddc2b91c75
Could you try to edit all these things using another browser than you used or another PC?
Maybe this is the reason of your problem.
Regards