Unimog Club UK

Pressure bleeding is far better than pumping with the brake pedal what tends to happen when pumping you use the full stroke of the master cylinder not normally reached as this means you may damage the seals or there may be some crud and that can cause damage to the seals .also when pressure bleeding if the flow of fluid is not strong from one of the bleed nipples this can indicate a fault with a flexy pipe as these have a bad habit of furring up.
Re fluid loss I have seen before now a brake drag causing heat to build up and boil the fluid especially if the fluid is old and contains moisture the boiling expands the fluid and pushes the excess out of the resivoir and not been spotted by the operator.
Always change your brake fluids every two years for the health of your brake at least.
Make sure your brake pressure is set right this requires pressure gauges and test points near the master cylinder figures should be on a sticker on the drivers door.
Moose