I have a website (access is open for you): https://haakbeest.be which is rather large with many plugins. It was fairly fast but not lightning fast so I installed Hummingbird + WP Super Cache and some other of your great plugins like Hustle and WP Defender.
Instead of speeding up my website, it went down to a crawling slow speed. I tried setting as much as possible (except for minification - did not activate that as it breaks my pagebuilder from Kallyas). Unfortunately it remained very slow so I turned to my provider. I upgraded to a faster server and more memory, ... just in case even though I was told my server was fine and should be able to handle the load.
Even with the increase, it still remains slow and the pagebuilder from Kallyas (example: https://haakbeest.be/?zn_pb_edit=true) fails to save - I see a 500 error in the console.
So I tried deactivating all plugins (including WPMUDEV plugins, especially Hummingbird and WP Defender) to restore the speed and restore the pagebuilder.
Each test I cleared the cache of both WP Super Cache and the Kallyas Pagebuilder cache. Unfortunately the website remained slow and also saving pages is still not possible (or actually it saves sometimes right before the error shows up).
My provider can't help me with this so I'm turning to you for final support.
On a side note: I also had CloudFlare installed, but I removed this and got my dns back directly to my server just to rule out that as well.
So as far as I can tell, I tried everything I can think of.
Do you have a way to figure out the page save error and the source of the slow website (both front end and back en)?
I hope so.