This is a reply from the seller.
Hi Martin,
I have spoken to one of my technicians and they have suggested that the Volvo's are fitting with a dim dipp feature, which is a half powered side light.
As LED's don't have a half power function, they will power on fully. Here is an interesting read from one of the volvo forums about this:
https://www.volvoforums.org.uk/archi.../t-201885.html
Sadly we are unsure on how to fix this as we do not specialise in Volvo's or have experience with them.
I'll look into this.