Another reason to dislike Lomo. Sorry to hear of your troubles. I doubt it is Foma film as I've shot loads of Fomapan 100 in 120 and never had this issue. As people are reporting this issue with Shanghai GP3, I suspect they are the supplier of this 'Earl Gray'.
How do you find the Holga? I'm tempted to buy one of the WPC versions to shoot 6x12, I'll remove the plastic lens and fit a Ross Wide Angle Xpress f4 5inch in shutter. The cheap plastickness of them puts me off, how bad are the light leak issues?