With the transmitter antennas fully-collapsed, the output stage of the module gets overloaded. The output transistor will heat up. If it gets too hot, it will fail. Lower range will show you if something's wrong. If range is unaffected, the transistor's working OK, but total service life may be compromised (it's not certain).

Just pull the antennal all the way out and then put it all back in except for the largest section. Leave that one out when you're programming or operating your transmitter for an extended period of time. You'd do this when you're setting up your system in the model on your workbench.