Sounds like still some air in the brakes, some bleed out easier than others...

Try a bit of heavy unbent coat hanger wire ~ sharpen the end to a seriously sharp point then use needle nose pliers to make a sharp reverse bend in it, poke a hole then use the bent tip wire to hook the rubber cap and draw it out....

Or maybe just ignore the damn thing is there's no resistance to the air volume .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better