Quote Originally Posted by Acetronics View Post
looks there's a supply stability or glitches problem that doesn't allow the PLL to stabilize quickly ... add a 10/22 µF Tantalum bead as close as possible to the PIC !!!
The only SMD tantalum cap I had handy was 1uF so I soldered it as close to the pic's supply pins as possible and it seems to have fixed the issue.

I'll know for sure once I've left it off night and turn it back on.

Thanks heaps for your help.