Android: Blokada freezes temporarily

1. What exactly is not working? Blokada freezes temporarily. This is noticeable in that previously blocked advertisements are then displayed. The "1" next to the app icon for activated blocking is no longer visible. When the app is called up, it no longer reacts and must first be closed. After a restart, the failure can be traced under the "Activities" tab. There are no entries for this period.
2. How to reproduce your problem (steps you have taken that caused the problem) Blokada is activated and runs in the background.
3. Which app version and which platform are you using? Samsung Galaxy XCover 4s (SM-G398FN) Android 11 Blokada 5.18.0 (via F-Droid)
4. DNS server issues are a common cause for some problems, have you tried selecting another DNS? No
5. Have you tried disabling DNS over HTTPS, or toggle other settings in Blokada? No

In some cases, before freezing occurs, Android reports that Blokada is no longer responding and asks how to proceed (wait / close app).