In the meantime I have been trying a few things to get rid of his problem
1) I followed Paola's suggestion to upgrade the FW from 2.1.2 to 2.1.2 with Fast Display Driver.
Which INDEED is much faster than the regular FW 2.1.2, but it did not resolve the issue of hanging (or loading the directory contents forever).
2) I formatted the internal memory and placed a brandnew system on it (which, by the way is also the FW 2.1.2 with Fast Display Driver).
See
https://www.mobileread.com/forums/sho...d.php?t=170994
Apart from being more confident now in handling the procedure of wiping the entire internal memory, I am sorry to announce that the old problem still exists.