Hello. Thank you for contacting the Toolset support.
I see you are using number of third party plugins. In order to minimize the cause of the issue as well as to ensure there in no theme/plugin conflict.
*** Please make a FULL BACKUP of your database and website.***
Could you please try to resolve your issue by deactivating all third-party plugins as well as with the default theme to check for any possible conflicts with any of the plugins or themes? Do you see any difference?
It looks like the problem was the new block-based widget editor that comes with the latest Gutenberg plugin (10.8.0 at the time of writing). I disabled Gutenberg (the separate plugin, which has features that are not available in the current WordPress version), and it fixed the issue. I suggest you start looking into this issue now, as the standard WordPress widget editor will eventually be replaced by this new Gutenberg-style block-enabled editor.