Doesn't keep accurate time

With my first watch it would loose approx. 10 min/day; because of this problem I returned the watch for a replacement. Now I am having the same problem with the second watch, except now the problem is the opposite, the watch is gaining 10 min. a day. I'm not a specialist but it seems that is some kind of defect in the timing mechanism. I would love to hear if anyone else has this problem.

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