Error: Try decreasing the “Max Page Size”

I’ve seen others run into this error as well:

An error occurred processing your request. Try decreasing the “Max Page Size”, or contact support.

I’ve tried:
* Lowering the max page size
* Raising WP_MEMORY_LIMIT to 256M
* Changing my PHP version

I’ve also tried this on different installs on this server. I still hit this error every time. My server’s on UpCloud, with 1G of RAM, and I’m managing it through RunCloud.io. RunCloud support is stumped as well.

The “Search & Replace” plugin doesn’t seem to have a problem, but it doesn’t seem to be maintained anymore.

Any ideas?