This is great information, I just had this service on my 2017 Chevy Colorado 31,200 miles. Thank you for the update regarding the GM bulletin.
I just had the same problem with my 2017 Colorado. Appears that it was a TCP shudder and is on recall. Not a safety issue per GM so not doing notifications of recall! Had to have the transmission flushed x5 and problem gone. Apparently the wrong type of transmission fluid was used when being built! Covered under recall so no charge to me.