I regularly notice that, after some time of work, clud sync stops working and always shows red cloud icon in the top right corner of Pro editor. Clicking on it shows window with pending uploads, and this is shown forever. Refreshing the page does not help.

This is rather dangerous because, as far as I understand, the project is only saved on the PC, you will not be able to open latest version on a different PC and if you clean browser cache, for example, you will loose the data.

This is independent of other tabs. If I have several projects opened in several tabs, one can have this problem while others don't.

In case it helps, here are some errors log from Chrome dev tools: