I missed this until getting tagged above, but it seems like the solution has already been arrived at.
Of course the battery can be discharged... but can it be done safely? I would argue no to that given the problem description. The Specialized BMS is proprietary, and you already know there is a failure of some kind, somewhere. It seems like its in a cell, but is it for sure? Difficult to say for certain considering the potential risk.
I doubt the 'Rejected' repair is due to being awestruck by the battery innards. More likely it is simply the fact that the proprietary BMS is just that, and any replacement is likely to be rejected... so why bother fighting with the customer if the repair doesn't work (the electronics that phone-home are probably also a factor)? I see this happen when I am reading private discussion between ebike retailers. They don't want to screw with the potential for backlash.
I am a DIY guy but I don't screw around with battery construction. I leave it to professionals, am involved in the performance specs and cell choice, and ensure I am dealing with someone who has a reputation for top quality. I can't say I would trust a 3rd party rebuild service without knowing a lot about them already from online commentary over time from satisfied or upset customers.
This is where you would want to be able to cash in on the extra money paid for the Specialized reputation. 140 cycles is awful as reliability goes, even if it is 7 years old. But I suspect they will hang their hat on that 7 year lifespan. We'll see.
