the cracked piece is the speed sensor on the plate, The two are hall effect sensors, - 2 wires that you see are common power and ground between the two hall effect sensors and two are the signal to the TCU - EGS module from each sensor.
when the connector bushing was installed, did the mechanic overtighten it by chance? - its a very gentle torque on the little screw (i use ATF on the O rings and push the bushing home by first gently feeling that the bushing it centered and the pins wont be hurt)
make sure the wiring plug is not damaged - the round circle plug on the cars wiring, - and use a small mirror to see into the connector itself that any pins are not damaged in any way. Also please tell if all the solenoids were installed correctly into valvebody - If the O rings were removed or replaced from the solenoids replacement ones can bulge out and block the exhaust side of the solenoids which can cause severe problems.
Also do tell if the solenoid connector pads were inspected and any markings removed.
I have had a similar problem once and it came out to be a bad wiring connector, the pins were not locked in it anymore, the connector is not too expensive either - and make sure that you wrap it properly with non sticky tape and end the tape with a turn of silicone tape.
One more thing - it is more than mandatory to use only a new genuine MB part or an equal manufacturer replacement and not any chinese useless replacement or a junked part, I have seen brand new chinese plates with bad hall effect sensors which I could only see with an oscope on the signal lines after the thing was installed, the sensor was sending erratic rounded top waveforms rather than crisp digital signal or sometimes would just stop working as the ATF heated up to 90C
when the valvebody was installed back, was it torqued back or "haath ka andaaza" - the valve body has no gasket between it and the transmission. The surface is microfinished to provide a good seal without a gasket and wrong torquing can warp it. - Get the codes out, (the deeper level codes) and then test the speed sensor signals with an oscope. You will get it solved.