The other option might be to knock in one or two wooden fence posts with the wee screw/nail on isolator clips ? That way he really can't pull them out

You can use the iron ones in between to save it getting slack.
I'm also wondering if you might need to up your voltage to your fence - it should be strong enough to be a deterent. Is something shorting it ? Or batteries maybe getting flat ? Might be time for the mains one

If it's a case of the grass being greener on the other side - maybe a change of scene (and paddock) for a while might fix it ?
Probably telling you how to suck eggs - but worth just checking

HTH
Karen
