gas leaks out of overflow vent whenever filling

Hey there, regardless how empty my gas is, every time I go to fill it with a jerry can after about 10 seconds it starts to bubble and come out of the overflow / air vent beside where you pour gas in... This just started this year after getting it filled to the max with gas on delivery from dealer. Any reason for this? It looks like the vent can be tightened and loosened. Which should I do?

I have to keep stopping filling it, wait 10 seconds, fill for 10 seconds, repeat... I've never had this happen before?

Thanks for any insight!

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