Widget Block error

Hi there, we have noticed a bug in widgets block.
When editing Widgets in Blocks will repeat with errors and the console shows it is a JSON error stating ‘The response is not a valid JSON response’ and also says 503 error with it.
Troubleshooting I have done:
– Have tried downgrading versions, errors will be removed but unable to move widgets around. Now I have the current version.
– Deactivating all plugins, one reactivated they come back and it is not related to a plugin.
– did permalinks,
– re did htaccess file
– classic widgets plugin also takes away errors but you cant move widgets.
none of these steps worked.
Some guidance on what is happening would be greatly appreciated. Thank you

• This topic was modified 3 years, 1 month ago by Steven Stern (sterndata). Reason: moved from alpha/beta/rc to fixing