The action might be too low. Maybe loosen the truss rod.

Thanks RG, I’ve had the same problem, interestingly it’s the same as Marc, the G string

I would agree, I recently was tweaking my truss rod and started getting a buzzing on the strings. It doesn’t take much try loosening it an eight of a turn to start

I was getting this on my D string. loosened the truss rod and it's good now. Helps for using a capo too.

I do like the low action though. Don't want to give the ole fingers anymore work than necessary.

I dont think is the truss rod...its happening on a Gibson j45, an Alvarez ap66 and a Mexican Strat! I'm really baffled tbh, I think I need to spunk up the cash and get a professional to look at it. Is hard to do though coz I'm so tight with money! It terrifies me that I may have to pay £50 or more

@cotton-eye-marc can you see where the string is vibrating too close to one of the frets?