HTML editor doesn't work

HTML editor doesn't work

Hi,
we have encountered some problems in Zoho Campaigns. We are trying to prepare a new campaigh but the HTML editor is not usable. 
After recent update of ZC the HTML editor has become very slow, it takes a long time to save changes, you can't undo recent changes, editing attributes of blocks causes them to be assigned to the block above.
It works disastrously. How should we prepare our campaign? After all, the HTML editor is a basic tool in ZC!