Filter don't work any more

Either Thunderbird filter function is extremely buggy, or there is something that I don't understand ... Some filters work pretty fine (though not always reliable) for years, an then suddenly they stop working. E.g. I have a filter (see screen shot) that's supposed to move all eMails with senders that are not in one of my Cardbooks to a special folder (Prüfen) and tag them. This filter worked for many years - well let's say fairly. About 50% of the Mails that applied to the filter rules were marked and moves correctly, 50% wasn't. And about 10% of the Mails marked and moved didn't meet the rules ... Seemed to be some timeout problem, because when applied manually it did what it should. Since the last update the filter doesn't work at all, when new messages are downloaded. If I apply the filter manually it marks all Mails, regardless of the rules - and it doesn't move any of them .... It's a rat race ... I already thought of deleting all filters in Thunderbird and do all the filtering on the Mail-Server. But unfortunately the filter functions of my provider are rather limited. Now I'm wondering: Should I change my Provider, or rather my eMail-Client or both of them? It's really frustrating ...