I suspect your RPM setting is too high for cutting the PVC trim board - under 15,000rpm is probably adviseable. PVC heats up quickly & likes to to turn into a sticky goop on saw blades/end mills/V-bits. The point of a V-bit isn’t able to do much cutting as it reduces to a sharp point & acts more like a drag knife at the very tip. The general rule with plastics is to cut at low RPM & high feedrate to cut actual chips & avoid melting the plastic. Also the reason for getting O-flute bits. I don’t know if there are single cutter, O-flute V-bits.
And if you search around the forum you can find some useful threads: