Ron, since the variable ports will automagically switch back to variable if you select the TR and change the voltage, it can be done by anyone with a remote.
You can also just cycle power to the TIU channel and it'll go back to fixed (until the next time).
It does seem that the Rev. L TIU's have had more specific issues with the variable channel FET's as well as much more frequently eating their 74ACT244 DCS signal drivers.
