I’m facing the same issue (in my case when importing a flex query from IB as described here and here.
The problem is that depending on the security, yahoo finance quotes are in GBX (e.g. IAG.L) or GPB (e.g. VUKE.L). Given that most brokers’ exports include GBP, I think the easiest fix would be to be able to manually include a factor ( /100) in the quotes dialogue in PP.