[slowsnake]

Geez, good luck with that mate, you must be aware of all the so called excellent bonding and epoxy products on the market, obviously you have some type of separation either through shrinkage, or the original application was applied and glazed over.
You may be right in assuming a silicone product, depends on the application.

Me, I would look at either sikaflex products or go for the old school "stag" jointing compound.

Bit more info would be good, and if its easily accessible to remove your '"trial and error" mistakes!

Cheers Billy.