Backend Insanely Slow

I’ve been using W3 Total Cache for a few months now, and my backend has been really, really slow. For example, when I try to access or save posts, it can take up to 30 seconds for the page to save and/or reload. When I turn off W3, the slowness goes away – so I’m pretty confident that this is what’s causing the problem. I’ve now got it disabled on my site.

Any idea what could cause this?

https://www.ads-software.com/plugins/w3-total-cache/