ERROR Updating failed. Error message: The response is not a valid JSON response.

Hi all,

So I’ve been experiencing problems with this error for a while (also before updating wordpress to the current version) and have done a ton of research on the internet. I’ve found multiple solutions, but none of them seemed to apply to my situation.

When does the problem occur?
The JSON error appears for me when updating pages. It also “corrupts” some of the blocks (using new builder).

What is different for me then for other users I’ve read about online?
This problem doesn’t happen on my PC, however it does on my client his PC when he wants to add or change images or text to the page. This suggests that the problem is caused by his computer rather then the WordPress site itself. However, it is still an error within WordPress.

I must say, switching to the classic editor will fix this problem for me. We would love to continue using the new editor, however.

I hope I have given enough information about my problem. If not, please let me know what you are missing!

Joppe.