BudgetAudiophile

Thinking about this a bit more... assuming the driver still technically works, I think the driver manufacturer was just trying to glue on a second coil magnet to couple the flux with the actual coil magnet. While the actual coil magnet is located with precision I don't think the one on the outside is super critical.

My ability to diagnose a finish/adhesive failure over an image on the internet is extremely subjective and limited. I can tell the failure was not likely to have been caused by the adhesive because of how it transferred onto the magnet. The driver side looks very suspect; like a surface that has had insufficient cleaning and prep. Professional finishes level cleaning prep is extremely rigorous. It is not quite chemistry lab/clean room levels, but it is unlike anything in a typical domestic environment.

It doesn't hurt to try this if you have the supplies: Clean both surfaces well with acetone or lacquer thinner, with the latter being the better choice here. Then use a sandpaper between ~180-600 grit, with 400 grit as my likely go-to, and take off all of the epoxy from both surfaces completely. Both sides should be a consistent matte appearance. Then I would use whatever 2 part epoxy I and find that is intended for metal, might be thinner in consistency, and has a long cure time. Use a piece of cardboard wrapped around the driver for alignment, get a consistent coating of epoxy across the entire surface and give it double the specified cure time or even more if the ambient temperature is low and/or if humidity is high.