Condensation in loft

It’s unlikely it’s to do with the gutters it’s most prob sky to do with air flow or ventilation and if you got the old tar felt it may have welded together on the laps during the heat in the summer causing less Air flow yes I would recommend leaving it open on a latch I would say you need roof vents or soffit vents fitted with vented dry ridge system

Nothing to worry over maybe just open the hatch

You have to decide what the problem is. If it’s ingress from a blocked gutter it would form a damp patch on the room below. Condensation would be beads or droplets of water to the underside of the roof. I think it’s fair to say it’s condensation.. The most cost effective solution would be ventilation. If you have loft hatches, open them up. External tile vents can be installed but in most cases will require a minimum of two in between rafters and be aware they can leak . Vented ridge tiles are perfect but not really a diy job. Dry ridge systems are good but again you need safety equipment and be confident in you’re ability’s on the roof. You don’t say what membrane you have( if any) or the type of roof covering. If you have a composite tile then ideally you would require a good breathable membrane and dry ridge. The best most cost effective product on the market are “ felt lap vents” but a currently hard to get due to a very high demand. I’ve fitted 100s with 100% success rate. Hope this helps.

Do not open the attic hatch up as this will allow more heat in to that area causing the boards to condensate even more, your roof is a cold area & needs to be kept cold, my recommendation would be to fit additional ventilation to allow air flow through the attic