There were lots of issues that have been fixed, that's why we release new versions that contain fixes. If you'd like to see, read the release notes that we create for every release.
Are you still using malformed lists expecting things to actually work properly?
i didnt know what a malformed list is and did not know that pihole has no fail-over for unidentify-able entries/content, and as i found out what lists that were i commented-out their entries.. and now i see no problem, except: the higher ram-usage: >73%, pihole-ftl according to htop: 67% ram, 695mb virt
but it seems much more stable than before - thanks to your all advices.. at least everything runs now lower than 'red-level' ( >90%) ..