Man TGA 2005: Automatic Gearbox Issues with Downshifting, Error Code 01086, Revolutions & Engine

Hello, I have a Mana tag from the end of 2005 in the machine and for some time the gears upward changes normally only with those down there is a problem Sometimes it does not kill at all, it only goes into revolutions and the engine starts to yell (usually from 12 to 11 and 10) then to N back to D and it goes. Manual gear shifting much better but it happens sometimes. error 01086
Thanks in advance for your help

Error 1086 is air system pressure No. 3. If the actual pressure is too low then the gearbox may be a problem. But if it's just an electrical fault with the wiring or the sensor, it has nothing to do with gear changes.
Pathologically .... up gears, even in a manual gearbox, will always come on, even without a clutch.
... and down, the clutch must disconnect the engine and the gearbox shaft must brake, maybe the gearbox brake is spilled, or the synchro is over.

https://www.elektroda.pl/rtvforum/topic2189867.html
https://www.elektroda.pl/rtvforum/topic2154543.html#10225308

10.2 pressure on the computer in the car. The worst thing is to stop and break down from 12taki to three. But going in manual mode, slowly changing gears down, is it ok
Which valves and where to find them are responsible for the pressure in the system

It is best to connect with manometers between the four-way valve and the pressure limiting valve and behind it.
If the gears enter normally with longer pauses between shifts, maybe some of these valves are not opening fully. The above test will confirm any pressure faults.