If it isn’t an installation issue as above, I’d check the frame for oval bearing recesses or splits. 50 miles is nothing and the bearings in my SC lasted over 3000 miles (Granted not the same model, but would expect similar)
How easy did the bearings go in? If it was very easy to slot them in, maybe the frame has distorted due to previous bearings being removed or installed incorrectly and at an angle.
The bearings were a pain to get out and just as tough to get in so I think the frame is good it’s definitely not the shock bushings had that on a few frames and I know it’s not that ,hope it’s not munkyboy that’s gonna cost and I only got the frame for £200
Not sure about the old 1.0 models. They have bearings in the frame instead of the link?
Anyway, on newer ones you adjust for play by adding more grease and increasing torque on the axle. Where the link has bearings and there’s an axle and cone washer with bolt, the axle is just done up snug but have to experiment to reduce play.
Worn axle you should see visible signs of on the axle and probably can feel it’s worn. Had one wrecked due to collapsed bearing, but it was cutting a groove into the axle and would have snapped eventually. Couldn’t get the axle on its own unfortunately, only the whole kit.
Though maybe ask Jungle. Their support is good and they sometimes can help out with odd bits lying around. I’ve had some stuff free off them, though cheap parts anyway.