E127 = Communications error between steering processor
and master processor.

This error can be triggered by static electricity, do the trucks have static straps / chains fitted?

The other thing to look at is the maxi fuses on both the hydraulic & traction frequency convertors, if the fuses look at all black / burnt replace them! Dodgy fuses cause all sorts of CAN BUS issue's on the older BT machines.

The last 50 x E fault codes should be stored in the fault memory along with the hour meter reading the fault happened, not sure if the time & date are also stored, been ages since I used the dash to view error's on one.

As for parameters, there are a lot of unused one's on the card as different BT truck's of that era used the same basic card with different software packages squirted in, in fact I've just looked & there is only 31 parameters listed in total for the Freflex BUT the numbers are NOT in sequential order, there are some gaps.