It's the gasket. This is a very poor design in reality, and frankly a stupid way of holding a crystal in place. Cleaning off the goop won't be easy, and I typically find alcohol does the job.
The paint on the underside of the crystal will come off when trying to clean it up, so really the crystal will have to be replaced, and they are now getting pricey with Omega jacking up the prices on the spare parts.
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