The problem was an over-current shutdown in the CC Phoenix HV 45 ESC. I was drawing about 90amps full throttle which was fine with my old setup on the Great Planes Lil Toni when using the Jeti 77-amp ESC. The Phoenix HV 45 didn't like it.

I reduced the prop size by an inch to an APC 13x6.5 so it now draws near 70amps at full throttle for about 1500 watts. On a 5lb plane, that's about 300w/lb! The ESC is rated for 2250 watts so it should be ok on my 6s Lithium voltage.

I also reprogrammed the ESC to disable current shutdown and low voltage shutdown as I'll use the DPM to do that. I have good air cooling on the ESC and will never need full power for more than a burst period so we'll see what happens. I see that Castle Creations has a "Castle Link" USB device for easier programming than the programming mode question method I used with my transmitter to set up the ESC.