Transmission shift problem (Euro Truck Simulator 2)

A small problem: often when shifting gears, sometimes to the highest, sometimes from 8th to 9th (10 speed gearbox) or from 4th to 5th (6 speed gearbox), the engine is constantly regassing, but transmission does not change. This is noticed when moving horizontally or on a slight rise. Downhill this is not, it switches normally. 13 steps. The checkpoint is behaving normally.
I changed the number of the differential, set the rev limiter, nothing helps. Who faced the solution of the problem, tell me, please, how to overcome.