well yea, thats the nature of a half step gearing scheme .. after all ..
the BWR hub has a bigger gap between the 3 gears than the BSR
then the gear switcher between the 2 cogs fills in the space .
its half, the IGH is the Whole..
Something more significant might be, the Gear Hub at the back might now be faulty. I am getting the Highest, and the one below, but not the third and final (i.e. lowest).
my guess** is the cable adjustment is too loose so It wont pull it into the low gear .
RTFM on how to adjust the cable ..
Hint : they call it an indicator chain because if in 2nd
the end shoulder of the shaft, that pulls on the gear shifter in the hub,
should be even with the end of the axle..
as you look thru the hole in the funnel nut on the end.
**A guess is all I can do since I'm, of course, not there..