Plugin causes admin permission error

This is a weird one. When sg-cachepress is enabled, on one multisite I am unable to save the WordPress general settings with the error:

You need a higher level of permission. Sorry, you are not allowed to manage options for this site.

Also the SG Optimizer settings page at network level is blank with a load of javascript errors.

I tried deleting and re-installing the plugin, clearing browser cache. There’s nothing in the server error log.

I have other almost identical multisites which work fine, so I’m assuming there is something in the plugin settings which is corrupt.