I had the same problem with my old 2006 STS-V. Went to the dealer three separate times. 1st they replaced the coolant senor, then they replaced the thermostat, finally they reprogrammed the ecm (there was an update around that time) and the problem went away. A thermostat is a very simple mechanical device so I find it hard to believe you could have a defective one. If you still have the problem after the new t-stat let me know and I'll dig up all the paperwork from the dealer to help you out. Good luck.
Yeah they're putting a 180 back in. The paperwork shows they tried to adjust the shift linkage with no luck fixing it. They suggested replacing the shift control assembly. Do you think the sensor needs to be replaced instead of the whole assembly?