A year ago I moved some cockpit winches before painting the cockpit
with LP. Fiberglass boat with 3/4" ply inserts in winch areas. I
drilled out the old bolt holes to new wood and glass, filled them with
West epoxy and their easy sand additive powder - and sanded them flat.

Now they've domed up under the 2 coats of LP and the 2 part primer -
you can see where the bolt holes were/are by the circle of thin bumps.

Any ideas why the epoxy "expanded" up like this. There was lots of
time between the epoxy and the paint - several weeks.

I'm going to do additional work - so would like to rectify these bumps
- probable redrill and refill - but want to eliminate a second batch.