@Kristof
WP Super Cache is a known issue reported several times in this forum – apparently the WP Super Cache plugin is not fully removed when deactivated and creates an ongoing error.
It looks like when I removed the "WP SUPER CACHE" plugin a few weeks
ago, it didn't completely remove itself and was throwing an error. I turned
on debugging mode and was able to find the error.For those who run into this problem in the future, please use these
steps if you've ever had WP SUPER CACHE installed...