Crazy Cruise Control Behavior (Intermittent)

Hi all,

I've had my 2006 for several years now, and have started running into several various problems along the path, but this one has started occurring more the past couple of years:
The cruise control on/off button turns the MFD "Cruise" light on and off, as it should. Normally, the cruise works as intended.

Sometimes, (usually on a warmer day when I left the windows up) when engaging the cruise control, it will either:

• Not "engage" and hold at the speed it should, slowing the vehicle down, which makes the "Cruise" light blink several times and then turn off
• Start slowing and accelerating intermittently in very weird ways (sometimes in a "stutter", sometimes just slower/faster randomly), sometimes even at WOT. Once, when it was acting up on a semi-deserted road, I set it to around 55 MPH, and it ended up slowing for a second and then accelerating at WOT to over 70 MPH before I cancelled it manually.

Any thoughts about what could be causing this?

I have replaced the clock spring recently with a Toyota branded one and all the steering wheel buttons work again (this problem has been occurring before and after replacement of the clock spring), and I don't think the brake lights are staying on (pedal switch), although replacing the brake switch was where I was planning on starting.
Also, it's not in "B" drive mode when this happens (for the person who seems to always ask).

 

Rock Auto
STANDARD MOTOR PRODUCTS CSP188
$210.14

 

I don't have a tech stream, I do have an elm Bluetooth adapter I might be able to view those from.
It did it this evening for about 10 minutes until I got on the highway and then stopped. It's so irritatingly intermittent.