Occasional leak from roof tile vent

[Tony59]

I have 2 plastic vent tiles on my roof. From within the loft, I see that their underneath interface is a 75 mm diameter pipe, presumably to allow connectors, or just to allow ventilation. One of them is directly above the loft hatch which is lined with polystyrene on top. The other one is above loft insulation. When I open the hinged loft hatch, once every few years, some drips of water pour down. I think that sometimes the wind blows the rain through these vents. The vent above the insulation probably drips water onto the insulation and that dries and disappears.
The vent above the loft hatch, drips water on to the polystyrene topped loft hatch, which pools there until I open it and get water dripping down.
When I inspect the vents, I see water residue or staining where water may be coming through.
I am considering blocking these vents, because the loft has other ventilation points along the top ridge of the roof that don't leak, as far as I can see.
Does anyone have advice for how to prevent the leaking?
It is unwise to block these vents? Or maybe I can somehow allow them to pass air, but not rain?
Are there adaptors for these vents to control how they pass air or water?
Any advice will be appreciated. Thanks.

 

[catlad]

I'd take it out.

 

[datarebal]

Condensing on the vent

 

[Tony59]

Thanks for the replies. Since it is well ventilated and there is no water source in the loft (no tank or humidity source that I know of) I didn't think that it could be caused by condensation on the vent. I am planning to block it with a thick plastic bag stuffed with a rag. I think that removing the vent would involve going up on the roof and installing a replacement tile, which I wish to avoid.