Thanks for testing. It would then appear that it's not a hardware issue at all.
@Eduma said in Duex2 Enstops:
Am I correct that in firmware 2.x you can not remap a home sensor to a different axis?
Kind of, but I don't think it affects their usage as triggers.
Using M584 to map drivers to axes does not affect endstop inputs. In RRF2, endstop inputs XYZ are pre-allocated, after that they are allocated in the order in which axes are created. So if you create just one extra axes (e.g. U), it will use the E0 endstop input. If more than one axis is created in a single M584 command, endstop inputs are allocated to the new axes in axis creation order (see previous item). For example, M584 C5 U6 would allocate endstop input E0 to the U axis and E1 to the C axis.
RRF3 does have more flexibility in how things are mapped, so if you wanted to test, you could create a very basic config using the online configurator for RRF3, update your firmware to 3.0 and then 3.1.1 and test your triggers. If it works, then you could migrate over, if it doesn't work, then you can reflash to 2.05.1 and use your previous config if you wish.
I'll ask DC42 again about the Duex2 endstops being used as triggers.