Yes, the Sprag clutch is probably slipping.
Sometimes the little springs that keep tension on the rollers get weak or break. One member here actually found replacement on the Net as a hardware item(not an ebike motor part)
Metal gears-They were all the rage a number of years ago, but nobody could stand the "dentist drill" sound 3 pr.s of metal gears produced. Using one pr. became the common practice for those that thought they needed them.
Why do you think you need them?
Since the original gears are fine, it's hard to see the logic of replacing them.
"If it ain't broke...."
'03 Rocky Mountain Edge 2WD 260 Q100H frt and Ezee V1 rear 2 Elifebike 20A & 25A 9-FET controllers 12S/20Ah Multistar Lipo rear 5Ah Turnigy frt Luna Cyclops Extra lite Alex 24DM rims, Crazy Bobs run ghetto tubeless. 25 mph. Mean Well HLG-320H-54A
'07 GT Idive 4 4.0, Q100C 201 14S LiPoly elifebike 9-FET 20A controller. 23 MPH.