Default E975 Stock 4.1.2 Hotspot turns on then off immediately

I recently reinstalled the stock 4.1.2 rom after the new stock kitkat update killed performance. Problem is now, I'm having issues with wifi hotspot. It was working previously on the stock 4.1.2 before I upgraded to kitkat. And as I understand, the international e975 version has no blockages on hotspot.

But now, when I enable hotspot, the icon flashes and changes blue for about one second before flashing again and turns back off. Wifi itself is working fine.

I have a memory of facing this problem about 12 months ago when I first got the phone, but I can't for the life of me remember how I solved it. Any thoughts? Surely it's must be a common problem if this is completely stock / unrooted?

Thanks in advance team