Problems with categoris and minification

1. My categories got completely messed up.

When I click on them on the Menu I either get Error 404 page or it sends me to a post with a name that begins with the same word as the category is called (i.e. category “flights” sends me to “flights to Australia”.

I tried disabling and enabling all the different caching options in General settings but the problem was eveident no matter what.

2. When I enable Minify -> HTML & XML my website does not load at all and I get the following message:

Fatal error: Unknown: Cannot use output buffering in output buffering display handlers in Unknown on line 0

Could you please help me with resolving these issues?

Thank you!

Best,
Martin

https://ww.wp.xz.cn/plugins/w3-total-cache/