500 Internal Server Error

Hello, I've been receiving "500 Internal Server Error" while trying to import site templates into into WP, (some templates, some import fine.)

I contacted my host provider and said: "we've checked the logs on the server, but we did not see any issue from the server-side, so there may be some internal issue with the theme, so we suggest you contact the theme provider and ask them to have a look into this as that will certainly help.

This is what's strange to me: I found a temporary solution here in the Generatepress forum support where someone mentioned to deactivate all plugins except for GP (which their hosting provider suggested them to do,) and worked!

And I say temporary solution because the issue persists in a different attempt to import for a different site after attempting the same actions.

Please advise.

Thanks!