What can that be?

Hi people! The old (GPZ) is stressing again. Had the same problem before about 300km: overflow of gaser 1u.2 dripped and it ran only on three pots. So the gaser bench out, sometimes in the float chambers looks et voila dirt between float valve Gaser1. Today (300km later) full gas on highway, highway descent down and again it ran only on 3 pots + fuel in overflow 1u.2. From where can the crap come? No rust in the tank to see, fuel filter is also installed & clean, Schwi Since these are the same signs as the last time, I assume that there is something between the valve again, but where can it come from? Had an old air filter that crumbled, but that rather gets into the engine and not into the float chamber. I have no idea what’s going on. Please help me! Greet Patrick