If there was a track change and the loop is right after a corner where it calls for hard accelleration, it could be bringing the voltage down to just below the point the xponder needs to run at. The BEC voltage of the QC series is lower than most at around 4.8 to 5 volts. It wouldn't take much to pull that down on a hard accelleration. Running the spektrum cap as mentioned could help.
The loop line itself could be causing problems, too. This was a problem at our track where some people were missing once in a while. Then durning the regionals, the loop completely went flat. After a ton of troubleshooting we replaced just the loop antenna that goes over the track and everything was cool from that point on.
Speed Merchant Rev7, Tekin, TQ Racing (wire), Team Tamale
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