[TYPO3-english] 404 redirect conflicts with cache

[Janez novak]

Hello,

This is my first post on this forum and I hope someone will find a solution to my problem, because I can't figure it out.

I upgraded a site from typo3 6.2 LTS to 8.7.7 and all works fine except 404 redirect 

My current LocalConfiguration is: pastebin.com/PJLw4zjf (I tried various options without success)

So my problem is this: When you write something that doesn't exist in URL 

- www.mypage.com/xyz => Shows homepage instead of pagenotfound.html
- www.mypage.com/xyz/xxx => Works fine (pagenotfound.html is displayed)

If I clear typo3 cache  then first variation (www.mypage.com/xyz) also works fine and 404 is displayed. This works until homepage is cached again. So after I reload homepage www.mypage.com/xyz shows me homepage instead of pagenotfound.html

I turned off cache on the homepage and now it works fine, but this is not a solution I want. 

Anyone has a hint or clue what could be wrong? I have another site with typo3 8.7.5 wich works without issues, so server configuration should be fine. 

Thanx for all the help