Unsuspecting with gearbox

Hello, now I’m completely helpless with my AR35. Have already created several topics about it but now???? Try to describe it briefly again. MV6 Built. 12.94 240000km. Transmission according to previous owner at 160000km overhauled (obs true?????) Friday evening completely normal driven.Saturday morning when starting only gear emergency run. At FOH error reading, solenoid valve 2-3 resulted open. Errors can then delete everything against normal. 2 days approximately later the same – emergency run and manually Switchable.Then over driving, the gearbox only switches in 1 and 2 gears and if you then over 4000 revolutions only comes in 1 gears.If you then restart again 1 and 2 gears up to 4000 turns. and then only 1 gears. Then in workshop (not FOH but one that also makes gears.) Let it read out there – again solenoid valve 2-3 open. The master said that it was funny but sure that it was on the solenoid valve. Oil should be filled up. Then the solenoid valve was made and new oil but no improvement.Then I asked if you also controlled the plugs on the gearbox and in the engine compartment-clear we said. Then new gearbox got which should be installed. Now I have today in the engine compartment the Blue Bajonet plug more often and put and at once it switched into the third but not in the fourth.Short time later it is then at approx. 5000 revolutions again in the first can it be that it is something electronic or that it was just a coincidence????