Horse changed overnight!

[Megibo]

Hi all I have copied and pasted from facebook on behalf of my mum:
advice needed, daughter is off swanning around Cambodia and her showjumper is out on loan. he likes to jump out of the field when he is bored or not being worked. the girl who has him is returning him as he has started jumping out on a regular basis and charging round etc. absolutely nothing in his routine has changed and we are clueless as to why he has suddenly starting doing this after 6 months of impeccable behaviour. the loaner has made the fences higher which he still jumps ( he is a hell of a jumper) if he can't jump out he just pushes against whatever it is keeping him contained, apparently electric fencing doesn't bother him. I think the only thing that will keep him in is stallion fencing. I can't have him at my yard as if he gets out he can get onto a very busy fast main road and I won't have him killing someone on my conscious, am clueless as to what to do with him as daughter has no intention of coming home and dealing with him and said give him away which brings it's own issues and im not 100% sure she actually means it!
other daughter and I are wondering if something has gone in his head to cause this but he is no different when ridden so not sure about that as if he had a tumour or anything he would be a dick under saddle as well.
any ideas as to what to do with him or does anyone want a horse who can keep him in or keep him contained in bloody high fencing!

 

[Polos Mum]

What has changed recently is the spring grass has finally arrived and he'll be getting a lot more energy from being out - can the loaner cut his hard feed right back to compensate?

I assume 1) he has company, 2) there is grass in his field so he's not hungry 3) he has fly spray so not being hounded out of the field by those nasty blood sucking flies that are around at the moment, 4) the loaner is being honest about why she wants to return him.

 

[ridefast]

Is he turned out alone?

 

[suffolkmare]

Probably stating the obvious and as a proven showjumper he'll have been out with loads of other horses at shows... but... is he "100% nut-free" and no in-season mares around??

 

[TandD]

he likes to jump out of the field when he is bored or not being worked. the girl who has him is returning him as he has started jumping out on a regular basis and charging round etc. absolutely nothing in his routine has changed .

he likes to jump out of the field when he is bored or not being worked.
so he is no longer being worked to the amount that your daughter was working him...so hes bored cos hes got nothing keeping his mind active?

the girl who has him is returning him as he has started jumping out on a regular basis and charging round etc
the girl is working him less and he has extra energy while also becoming bored

absolutely nothing in his routine has changed
bar the amount of work the horse is doing?

it just sounds like he wants more work - jumping is fun and he wants to do this...... can you do any more work with him?
my gelding was jumping fences, galloping around, playing with every horse he could fine till he came back into work last week, where he has stayed out from 8am till 5pm with no sight of any of this above behavour!