DM mode breaks

The new semi truck has a DM mode but the shift logic breaks. You should be able to shift back into drive immediately no matter what manual gear your in because apparently that style of automatic transmission locks the gearbox so it cant upshift but it can downshift. For increased realism I should be able to go 50. Put it in Dm mode and it stays in that gear if unable to downshift. It can downshift but its like a ratchet unless you release the ratchet strap latch the strap will stay tight. The new semi truck I guess works the same way realistically. I should be able to shift back to D. Not go from m(insert number here) all the way down to m1 before shifting back to drive.
I was on east coast fully loaded with my 8x8 and was going downhill but apon reaching for it I shifted to d but it went from m4 to m3. To m2 and then m1 redlined the engine extremely which the real life transmission shouldnt do. It should jump straight from dm to d no matter what gear its in theres no paddle shifters so controlling the gear its in is pretty unrealistic. Its a little different than the automatic low gear of the american semi trucks. Similar but still different. Please fix it