Problem with tags - wrong tags assigned

Hi, I have an issue with messages being tagged wrongly. I have first set up a series of custom Tags (Clients) and then I created Message Filters, Applied when getting new mail

From contains example1.com --> Tag Message "Client1"

From contains example2.org --> Tag Message "Client2"

From contains example3.edu --> Tag Message "Client3"

From contains example4.es --> Tag Message "Client4"

The Message filters seem to work correctly according to the Filter Log, i.e. a single, correct tag is Applied to the message.

HOWEVER, in the message list, some messages have two or even 3 tags without any logical explanation.

Any idea what could be happening? Let me know if you need any more info

Thanks!