Two options are available for releasing tetherless operated locomotives.
These options are set by DT400 Option #3.
No tetherless release allowed:
if the LOCO Key is pressed while the DT400/R is running in tetherless mode, the addresses selected will not be released unless the throttle is plugged in to LocoNet.
This is the factory default.
Tetherless release allowed:
if the LOCO Key is pressed while the DT400/R is running in tetherless mode, the address selected on that side of the throttle will be released immediately and that throttle will become inactive.
To re-select this loco address plug your DT400/R in to LocoNet and select the loco address on the throttle.