[FTC]: TETRIX DC Motor Gearbox issues

[Wingus&Dingus]

So we've broken a couple of lift arm motors.... both V1 and V2. Mostly gearbox destruction.
We're reasonably confident everything we can do to prevent this happening has been done but we struck a new issue this morning.
If there's a loss of control due to communication issues sometimes motors get left running at whatever power they were last set to and with our lift arm that's not a good situation. Under normal circumstances the arm won't ever hit the mechanical stop points at full power (actually it's limited to +-70) and there's position feedback and limit switches so all is well but if communications stops we can quickly end up with another busted gearbox.

Do we need to manufacture a clutch so there's a last ditch mechanical safety system?
Has anyone else struck a similar problem and what did you do about it?