Problem with gmail and its filters

[fluidistic]

I'm having a problem with gmail. I am subscribed to a mailing list (of Maxima software) and I've set that every time I receive an email from that mailing list, the email should appear under the label Maxima and nowhere else. However it also appears under the category "forums", even though I've never set those emails to appear there. I've rechecked my filters, deleted them and recreated them, to no avail. The problem remains and all emails from that mailing list appear in both "Maxima" label and "forums" category.
How can I fix this?

 

[Greg Bernhardt]

I know that Gmail's auto labeling can be frustrating at times, but I find it strange that the email has two labels. I would post the question here: https://productforums.google.com/forum/#!categories/gmail

 

[fluidistic]

Thanks for the suggestion. I'll post there.
The emails have only 1 label (Maxima as it should) but is also wrongly sent into the "Forums" category (which differs from a label if I understand well).