time pausing during races ?

Doclad said:

I think it pauses when watch is briefly out of sight of the GPS perhaps?

Unlikely.

You'd be surprised how often the official race timing system is operated sloppily by race officials, especially for less prestigious local races. Other discrepancies might come from the fact, that some races are timed from the starter's gun shot, while others are timed from the moment the chip crosses the start line. And I've even seen things like for example the finish line timing mat placed several dozen meters before the actual finish banner. So if you don't know exactly how the race is timed, then you might be pressing the start/stop button at the wrong moment.

What I'm trying to say is that most likely your watch's timer works correctly, and any discrepancies come from differences between what is timed by you and what is timed by race officials. And it is actually quite easy to verify. Next time - not necessarily during a race - take another timer on your run - a regular stopwatch or your smarphone will do. Start both timers at the same moment, and after the run stop them at the same moment. And then you'll know if your garmin gives you correct timing.