Skoda / Octavia / 1,4 TSI-140KM - RPM when pressing the clutch

Hello.
Skoda Octavia 1.4 TSI -140 KM-2013-103 thousand mileage. When stationary, pressing and releasing the clutch, the engine speed increases automatically to about 1200 rpm and after 2 seconds it normalizes. The increase in speed occurs both after pressing and releasing the clutch, but not every time (in most cases about 75%). Interestingly, the described increase in RPM does not sound like a normal addition of gas, but like the acceleration of a choking engine. I have the impression that a similar increase in revs occurs with each gear change while driving, which in turn gives the impression that the gearbox is not smooth. Jerks, like a novice driver. Coupling takes place at an uncontrolled, temporarily increased speed (I drive over 30 years / tenth car). When the clutch is released, during normal gas addition - everything is OK.
The car idles smoothly and stably.
The car on the site, under the computer does not show errors. Attempts to replace the clutch pump and clutch position sensor do not give positive changes.
Please comment.

I press the clutch and keep it depressed The revs rise when the pedal is pressed to 1200 rpm. and after 2 seconds they drop to normal. The clutch is pressed all the time.
Then I let go of the clutch and the RPM increases again to 1200 and after 2 seconds it drops to normal.

Hello.
In the service, repairs are made under the warranty. At the beginning, the clutch pump, the clutch position sensor, the slave cylinder were replaced (apparently) and finally the software update was uploaded. It took a while, but the fault was removed.
Thank you colleagues for the hints and best regards