Hey, I just bought my first Volvo a few days ago. It's a 1976 244DL. Everything seems to be working more or less fine, except there's something weird going on with the brakes. When I'm stopped the brake pedal starts to slip and the car rolls forward a bit unless I put more pressure on the pedal. Also occasionally when braking the brake failure light comes on though the brakes continue to work. It goes off when I accelerate and lightly tap the brake pedal again.
I know very little about cars, so excuse my ignorance.

Anyone got any ideas what this could mean.

Do you have power brakes?

the car has 2 circuits and the light tells you pressure is different, so one circuit is bad

is fluid level same in both sides of reservoir?

sounds like you need a new master cylinder

Brakes normally corrode such that the cylinders and calipers need replacing every 14-15 yrs unless re-sleeved with stainless steel bores.