'93 Rangie, KA635019 VIN with ABS, RH drive..

Brake lights stopped working on rear corners, one in center of upper tailgate worked OK.

1. Checked globes OK but replace anyway.

2. Checked switch OK, but replaced in case of intermitant fault.

3. Flashers, parking, reverse and tail lights all working OK.

4. There is NO power to the stop light at the tail light assembly harness plug near the tail lights.

5. While doing some testing, the stop lights came on for about 30 seconds then lost power again now the one on the upper tailgate stopped working, globe is OK.

6. ALL testing done with digital multimeter.

All light related fuses appear to be in fuse box on facia in front of front passenger seat, I have found 2 more under the drivers seat ALL FUSES TESTED OK.
There are plenty of RELAYS scattered about the cabin but there is no indication what they are related to, I have been able to work out what some of the are for but none seem to be stoplight related (But who knows?).

Does anyone know if there are any STOPLIGHT specific fuses anywhere or have electrical details (Schematics) for this model that I can download.

Thanks in advance for any assistance.