My guess is that its just a standard 4004 diode thats used as a block to prevent wash going back to the driver chips should it go short... looks to be the case, banded side to transistor.
Depending on what they are.. you could replace with a standard transistor ( TIP102, BC548 etc) and place a diode on cct from leg to pad.
Its not totally necessary... no other machines ive ever seen have this package design for protection. Just bear in mind that should the transistor short in future, there is nothing preventing it taking out the chip next up the line.
remember.. this was the most common cause of Spider chips failing on GTB Sys1.. simple diode protection would have prevented it
