Meritor Auto Transmission

[Bobsuruncle]

We have a 2005 Freightliner with a Meritor 12 speed transmission. It shifts fine for the first 8 or ten miles then when we shift out of drive to neutral it goes into SM mode. We had the TCU on the transmission replaced and it's no better. Freightliner in Stoon don't have any answers. I have discovered that putting the pto on before taking it out of drive stops it from going into SM mode. Also discovered that a specific sequence of shifting the gear shifting paddle into and out off neutral and drive that I can get it out of SM mode. Does anyone know of a shop or mechanic who has a lot of understanding of how these transmissions function because Saskatoon is stumped and we don't want to just randomly throw thousands at this transmission hoping to stumble apon the problem. TIA.