After disconnecting the shifter cables from the transmission, I tried to engage 5th and 6th gears manually (car on jack stands) and after several attempts
only once managed to engage 6th... this shows that it is an internal issue and not cable related.
Yesterday I called two specialty shops, both of them specialize in Porsche transmissions: GBox mentioned that it could be a broken shift fork and the other shop California Motorsports, mentioned that it could also be a broken retaining clip, and either way the transmission has to come out..
For reference are the numbers 6 and 7 on the attached picture.
Threaded Mode
