Truck Repair: Freightliner ISX500 get randomly stuck in 2nd and reverse gear

Question
I have a 2009 Freightliner ISX500 Argosy. I would like to get some advise on the problem of getting stuck in gears (automatic or manual). The problem started about 3 months ago with the gearbox got stuck several times in 10th and 11th gear. The agents for Freightliner in Namibia replaced the gearbox controller and xy selector with various valves on gearbox. This made the problem better, but it still randomly gets stuck in 2nd and reverse gear.

When the gear gets stuck, all I need to do is to move the truck for about 20-40m (forward or backwards depending on which gear it is in) and it will automatically correct itself. This, as you can imagine is a huge problem when you move in small spaces. The error on the display indicates flashing "Check transmission" and F2 ör FR flashing. It won't allow me to change to Neutral, and with a loud beeping sound it will remain in gear.

Thank you for taking time to give me your best advise.

Answer
i'm guessing what you have is a eaton autoshift. That's what freightliner normally uses there is 3 sensors on it two in the top plate for your countershafts and one is your tailshaft sensor. We've had a lot of problems with those sensors acting up. That's in Volvo trucks a eaton auto should be the same regardless of what truck it's in. Another problem we've had is the transmission harness the newer harness has some kind of capacitor in it that the older one's didn't have. That's a small harness goes from those three sensors too the transmission ecm. I would try the sensors first.