New BB58 not wanting to restart - question for the experts

[Devildog]

Hi all

I know the simple answer is send it in under warranty but I'm curious as to why it might be happening

Watch is 6 months old. Never dropped, knocked or subject to any shock loading. Totally unmarked. Running about + 4spd dial up overnight, pretty much dead on on the wrist or crown up overnight.

Gave it a full wind and it stopped 65 hours later. Not quite the advertised 72 hours but not bad.

But, couldn't get it to restart. Normally after a few winds it will run, but not this time, gave it 30 or so winds, second hand advanced a few seconds and stopped. Gave it a gentle shake and the same.

Wound it until I could feel the mainspring slipping in the barrel and kept going for a few more to be sure. Nothing.

Gave it another shake - nothing. Gentle tap, advanced a few and then stopped. Gave it a couple of sharper taps and still no joy. A couple more and eventually it started.

Hacked it to set the time, pushed the crown back in and it wouldn't start again. Another few sharp taps, another few stop starts of a few seconds and eventually it started. Ran fine all night in the box and has been on my wrist all day. Holding time fine. Might be running ever so slightly slow bit I'll check that today.

I fully appreciate that its a mechanical instrument and that sometimes more toque than is available from a partly wound mainspring is needed to overcome gear lash, etc, but its never done this before.

Any watchmakers/experts able to opine on what might be wrong?

Cheers in advance