Larry, I found ultimately a way to produce the crashes reproducibly. It seems
indeed that the expansion board worked only properly in the "bottom part". When
filling up progressively beyond approx 1.5 Mb i. e. 0.5 Mb only on the board,
very little would produce a crash and additional programs would no more load.
Some even gave the message: "Out of memory" although there should have been at
least aniother Mb. I pulled the board out and brought it back. The shop was not
pleased, as they just had a little dispute with Commodore and stopped to sell
all Commodore products. OK let's see what happens. – Alfred