ya... they increased the diameter of this protrusion a year-ish ago. ( probably to make it stronger )
You have 3 possibility:
1- Ask your KMX vendor for the older component that have a diameter of 19.7mm ( they may no longer have that version though )
2- Buy a cone drill bit 4-22 mm and re-drill the new spindle's mounting hole in order to reach the 22mm diameter on that side only:
I found the cone drill bit on Aliexpress for less than 4 us$ shipped.
If you go that way, make sure to hold the suspension in a big vise ( use a rags each side to avoid damaging the screw's head finish ) then drill at a low rpm. ( hold the drill with both hands )
3- Bring the old KMX spindle piece to your local welder and ask him to sand blast the paint and weld a line where the crack formed. ( buff the area in contact with the suspension adapter if needed )