I just got back in the hobby after being away for 5 years so I'm using an older Spektrum radio and receiver and am wondering if this has anything to do with my question.

Here's what I have:
Spektrum DX3 radio (original one from ~5 years ago)
Spektrum SR3000 Receiver /w Voltage Protector (original one from ~5 years ago)
Tekin RS Speedo
Tekin Redline 17.5 motor
Associated FT SC10

I was able to calibrate the controller without issue, everything appears to be working fine. Truck runs great, no glitching anywhere. My question is concerning the LED flashes and what they mean.

When I turn on my truck the speedo boots up and LEDs 345 flash, it's my understanding this indicates the speedo is in "Spec Lockout" mode, which is fine. Then after LEDs 345 flash LED 1 flashes. The LEDs cycle through this sequence regularily but every once in a while all seven LEDs will flash and then it will go back to the "normal" 3,4,5, then 1 cycle.

http://www.teamtekin.com/rs_troubleshoot.html

Thanks for the link, I looked at that before but the code I'm seeing isn't constant flashing of all seven LEDs its just a quick flash. I'm going to assume its the radio signal,I had planned on updating the radio in the future but it looks like that might be needed sooner than later.

I dont think your radio has anything to do with it. I ran a Futaba 2PK 75MHZ radio for a couple of races and didnt have any problems.

Do have a couple of questions.

What is you gearing? Could be getting a little warm and the built in temp sensor is showing on your LED's.
Do you have a cap soldered on the posts of the ESC? You said you have on in the RX, but the ESC one is good to have as well if not better.
Worst case sonerio, reset you ESC, callibrate it with all of your transmitter settings at 100 and re bind your RX.

See what happens from there. Sounds like a throttle dead band or nuetral width setting is off just a bit causing the LED's to flash.