I trawled the threads but couldn't find it. All the related threads are about external colour transfer onto bags, so clearly not a common problem.
As you're in the UK it's unlikely to be related to humidity, so chances are you have simply been unfortunate. A lot of ladies use liners (Samorga is very highly recommended, but there are several brands - type "liner" into the search bar to find them), the rest of us tend to prefer to use pouches to organise the interiors of our bags and ensure no colour transfer. So that might be something to consider.
As it appears not to have been a problem it's difficult to suggest the best course of action. If you really love the bag, I'd opt for getting it sealed.
Thank you for all your help, I'll take it back and get it sealed, I may ask them to replace it again though, since it does seem to be an odd case.
Have a nice day.
