Not so the first time I filled it, and not so with the port tank. The vents appear to be clear.
Wow! I had the same problem. Tank filled fine until last summer then the starboard tank could only be filled at a trickle. Turned out the vent hose was too long and had a sag which got a slug of fuel preventing air from escaping during filling.
Solution was shorten the hose and make sure it rose from tank to vent. Hope you have good access.
North Pacific 39