Makes me think its more to do with the clutch.
Clutch fork bent or worn
Dead hydraulic fluid making it spongy
Slave cylinder needs an overhaul
Or the system just to be bleed
It reminds me of the time with my ex's ae82. Had a real bad vibration around the 105km mark. We kept taking the car back to get the wheels balanced this way, that way and every way in between, nada absolutely nada no difference at all till i had to swap the drivers side driveshaft cause it started clicking.
SoulSearcher, just like what KE30_KE35_KE55 said with Consumer Affairs, i'd be asking them about it. But by rights any work done on your car (be it mechanical, body, electrical) should be covered by a warranty.
Or if you want South Oz Ombudsman to help with pointing you the right direction.