Thanks for the suggestions so far. I will have some troubleshooting ideas for today.
For the receiver issue: if the motor draws too much from the batteries, does it reduce what the receiver can use and cause glitches?
The batteries I'm using are NiMH - GP3300, built by a local racer (I bought them used) who is on nipo now. I have 3 different packs, all the same, and I've had this with all of them.
Please keep the suggestions coming in, I'm going to start in this order:
1. Charge all batteries to peak and run them
2. Switch out my receiver for my son's Traxxas receiver and test
3. unsolder the bullets and directly connect the ESC & motor (am I risking anything but convenience here?)
4. Resolder the deans to the ESC (I did this myself, but a racer checked it out last night and thought it was fine)
I am running the ESC wire underneath the batteries to the receiver (the T4 was designed to do this). Any potential issues here? I guess I'll make moving that #2 and try moving that around the front near the servo.
Also, the solder we used with the Dean's wasn't the stuff you can buy online. It's this:
The connections hold... forgive the perhaps silly question but it wouldn't be the type of solder, would it? That stuff looks close, as least. It has double the amount of silver as Dean's solder from listed on hobby web sites.
I'm grateful for the assistance. I'll be able to spend a few hours on it today and hope to report back the solution soon.