Intermittant problem saving posts

I’m being faced very often when I typically go into a saved draft, edit a post and then save it. I’m getting the error:

Updating failed. The response is not a valid JSON response.

I’m finding that I can often publish, but if I continue to save as a draft, I may or may not get what I was expecting. I’m seeing titles disappear and other pieces of content. I have reached out to WordPress and was told to change the ‘permalinks’ settings and then change back again. This did not work. I was also told to roll back to classic editor, which seems to work, but I want to continue using blocks. How can I resolve this issue without having to downgrade wordpress for our writers?

As was suggested here is the debug below