>>320541914
The trackpad sensor will inevitably fail. The sensor is kept in contact with the touchpad itself by nothing more than a shoddy rubber pad, which will either slide out of place due to shitty glue, or be compressed down over time and inconsistently read signals. Disassembly of the entire controller and adding additional padding is more or less mandatory, to the point I did it dozens of times before Index released, just to be able to move around in games without having to exert upwards of 100lbf on the damn thing
The ribbon cables inside the controller are incredibly fickle- if they don't unplug while you're disassembling the controller, they'll tear internally, which is not only entirely impossible to repair but extremely difficult to avoid. This will do such fun things like disabling random buttons, completely bricking the controller, or fucking your tracking, despite none of the affected by disassembly being directly attached to the ring.
The tracking ring itself is only attached by a slim piece of plastic bolted to the main chassis by two slim screws. Any impact of the ring against a surface will likely fracture that plastic and the tracking ring will become loose, and assuming you don't also tear the ribbon cables connected through that slim point, the loose ring will make any sort of precision impossible as the signal from the controller flails wildly from minute motions. 

Oh, also- there's no warranty service whatsoever, no refunds, no tech support. Do it yourself or buy a new pair, or, in this case, Index controllers
The former Oculus users who migrated to Index and incessantly bitch about the controllers don't fucking know what they were missing, an irritating stick issue with unlimited question-free RMA with advanced replacement is oh so awful and the Index is a flop