Read the manual front to back several times and there's no mention of this LED condition. Also checked www (dot) teamtekin (dot) com/esc_codes.html. The "FAN REVERSE POLARITY" condition there is the closest thing, but that sequence is 6, 5, 4, 3 and I'm definitely seeing 2, 3, 4, 5. Also no fan for me.

It's actually a very old Airtronics 3 channel FM receiver (92736) with a Caliber 3PS transmitter. I'm not wondering if the throttle signal from the old receiver isn't compatible with the new ESC? Haven't been able to find mention of compatibility/incompatibility either, though ..

I should also note that the speed control doesn't respond to any button presses when cycling the LEDs (can't go into radio calibration or even do a factory reset). If I unplugged the receiver, I get the appropriate error code for no receiver and am able to do a factory reset that way, however.