Fastest cache slows down WP Backend

Hello,

i’ve installed Fastest cache on my client’s website and it slowed down backend a lot.

When any of the cache options are active, i need about half a minute to load any of the backend parts.

When i turn off all cache options or i disable the plugin, backend works fine.

Plugin also needs a lot of time to activate again. Way more then any other plugin i have.

Can you please help me with this and let me know what could be the problem here?

Regards