The 1A contactor is what allows for high speed travel. In the line of 5 contactors it is the center one. It is possible the contactor went bad, the resistor across the contactor winding is bad, or the contact tips are too worn to make contact.
If the contactor does not try to close when requesting full speed travel, it is one of the first 2 options. If you order a new contactor it come with a new resistor.
Typically I just replace the full contactor as they do go bad over time. PN: 090304