I think some are confusing the old bushing system with the newer bearing system. The old system required loosening the grub screw, tightening the large bolt on the opposite side then re tightening the grub screw. Worked well too, in 3 years I only had to change the top hat style bushings twice, all other bushings were still fine.
On the ION’s it’s a new system of bearings that are not adjustable and once you have ruled out other possibilities such as shock bushings and loose bolts it’s new bearings required. Except for the rearmost part of the linkage on the chainstays, they are as per the old bushing system and should last donkeys years.