I just talked with one of our engineers, this is what they had to say:
It could be a broken CC line on the L5 or it could be a crap cable.
Getting a trace using the debugging steps here https://source.puri.sm/Librem5/firmware-tps6598x-nonfree might help (identifying what's going on)
@dad
In case of HW issue (broken CC lines) please get in contact with support (and tell them your order number).