What did you replace the clutch master with? New, rebuilt, rebuilt yourself?

As to what happens once in a while, my theory...The seals in there when relaxed when just sitting there. When you press the pedal they come under pressure and seat themselves, or in your case, seat themselves most of the time. If they don't seat the fluid just goes by the cylinder and you have to pull it back and try it again. And that theory would apply to both master and slave.

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5 speed '91 190E 2.6 320,000 mi. (new car, fast, smooth as silk six, couldn't find any more Peugeots)
5 speed '85 Peugeot 505 2.5l Turbo Diesel 266,000 mi. (old car, fast for a diesel, had 2 others)
5 speed '01 Jetta V6 (new wifes car, pretty quick)
5 speed '85 Peugeot 505 2.2l Turbo Gas 197,000 mi. (wifes car, faster, sadly gone just short of 200k )
5 speed '83 Yamaha 750 Maxim 14,000 mi. (fastest)
0 speed 4' x 8' 1800 lb Harbor Freight utility trailer (only as fast as what's pulling it)