zOwie Omega Discussion Forum

I had the same problem and it had to do with my diver's extension not being properly closed. I copied this from the troubleshooting section of this site. I hope it helps:

The Seamaster Pro bracelet clasp may not stay closed tightly. There are two causes of this problem.

By far the most common cause is if the diver's extension is not closed properly. There is a small flange at the hinge of the extension that must be tucked under the metal crossbar when the extension is closed. If not, the extension does not close flush, preventing the main clasp mechanism from closing fully. If your clasp keeps popping open unexpectedly on you, this is likely the cause.

A very small number of Seamaster clasps have had slightly weak springs that prevented the clasp from locking as securely as it should. This is easily corrected by an Omega service center. Omega has already updated the design of the clasp to eliminate this rare but annoying issue.