http://sn.1w6.org/file/mk-20161106T173321-naqff7u.html
@mk my final analysis is that the 'unreadable' symlinks resulted from a series of botched updates of sasl2. If I remove them there is still a directory with the sasl2 files left, identical to those on the host system. That insight only took most of the day to reach. :) I declare !beer o'clock now! :-D