The only watch ever that quit working while on my wrist for no apparent reason is that unhealthy combination of a cheap Eta ticker with a non-fitting chrono module. I've talked to several very knowledgeable guys within the trade (who downright refused to try servicing it), and it basically comes down to the unfortunate facts I'm quoting here from another website, as this is the last effort I make regarding an Omega (Obviously Mechanical Garbage) Automatic Redux: Stay away, pals. You don't want this piece of ****.
"I've heard privately from several different people who have talked to watchmakers that the chronograph module in the reduced is a exceedingly difficult one to service... The time module, which is essentially a SeMP (non-chronograph) movement is is not at issue, however the word on the internet is that the chronograph module is nearly impossible to service or adjust for even the most technically adept watchmakers who speed though other common Omega Movements (c.321, c.x86x, c.1040, c.1041, c.1045, 7750's, etc.)... At least one watchmaker is known to just mail the chronograph module to Bienne and ask for a new module complete, which Omega will send, no questions asked, for a cost of around $140 US. Apparenly it is significantly less hassle to pay that cost than to work to repair the module."