Hi Paul, welcome to the fold
We store our beans in old Illy tins too.
I Once was told that the beans after being roasted need to be de-gassed, thus the reason for the one way valves on the bottom of the Illy tins and also the Coffee bean bags.
The beans will sometimes go a bit oily (I find it worse when I have over roasted the beans)
But I think even Rich and Rae used to just store their roasted beans in those tins with the lock down lids (rubber seal and lever action clip to hold down the lid) but even those tins dont have a one way valve.
So my un professional thought might be that you need to reduce your roasting a bit..... But remember that the beans do emit some oil, but someone else might know something I dont
Regards and good luck