In this thread https://mbworld.org/forums/gl-class-...ml#post7837965, forum fellow "tadiguy" mentions cold solder joints as being a possible culprit for intermittent ESP Inoperative errors. He also wonders whether a loose connection between the stalk cluster and the steering column could be the culprit.

I've had intermittent ESP inoperative errors for a while now, and decided to try to tackle them for once and for all. I bought a replacement SAS, but wanted to avoid installing it as I wanted to be sure of root cause.

I don't think either of tadiguy's possibilities would create the intermittent ESP Inop messages. Here's why:
1) The SAS module consists of a motherboard that communicates with the rest of the stalk cluster, e.g. the lights stalk, the cruise control control, and so on. The "push-through" connectors he mentions go from the motherboard to other stalk controls, not the SAS itself. The SAS itself seems to be cleanly soldered to the motherboard.
2) The connector between the SAS motherboard and the steering column is a data bus, just a few pins. If it fails, it would fail catastrophically, with errors in the airbag, radio controls, and so forth.

So why does the SAS go bad like that? You got me. It's an optical component, so ... light leakage in? Dirt on the optical pieces? I cleaned it carefully, and the ESP Inop message didn't come back, but it wasn't on before I disassembled in the first place.

Here are the disassembly / reassembly instructions for anyone who wants to mess with theirs:
1) T-30 screw (2) hold the airbag / horn button module on from the back side
2) Unclip the wires from the airbag. The green and orange clips have a latch mechanism; pop it out and the connector slides off. 3rd connector (black) goes to the steering wheel and unplugs easily.
3) 10mm hex screw releases the steering wheel.
4) After removing the bolt, mark the splined shaft and steering wheel for reassembly in correct position.
5) T-30 screw holds the stalk cluster to the shaft
6) Pull stalk cluster straight out, unplugging the bus connectors.
7) T-10 screws (x3) hold the winding pass-through connector on top of the SAS, which can now be removed and disassembled.

For reassembly, note that there are instructions printed on the SAS on how to realign it.

When I first reassembled, I noticed the shroud was way off angle. it turns out the whole assembly that the stalk cluster attaches to on the steering column is just held on by friction. Tap it with a hammer and over it goes.

 

Failing wheel speed sensors are also a leading culprit of ESP errors.
I'm also not sure how OP in the OP traces his ESP errors to the SAS without a code readout.

 

I actually got steering angle sensor errors. Dunno about tadiguy's experience.

It's a pisser when errors are intermittent.

The optical sensor is one goofy over-engineered piece of ****.