Blank page (only works if I disable gutenberg)

I have searched the forums and googled this a lot but I cannot find a good solution to it. It started when I updated the wordpress version I think (not sure though).

I cannot access the add/edit post/page. It will only show up as a blank page.

I have tried several things – without fixing it, for example:
– Activate “Health Check & Troubleshooting”-plugin and it’s debug-feature
– Disable plugin by plugin, and disable all plugins
– Change to default theme
– Etc

The ONLY thing that got it to work was by installing the plugin “Disable Gutenberg”. However this is not a good solution for me, as 1 would like to use Gutenberg and know what the real issue is behind the blank page. Also, disabling Gutenberg breaks the SEO Yoast-box which I like to use.

Anyone know why this happens and how to fix it without having to disable Gutenberg? (Note: I dont use the Gutenberg plugin, I use it from WordPress’ own incorporated one since I use the latest WP version).