Strange tachometer behavior
 

Hello!

Got my Mazda 3 two months ago. Have recently noticed a strange behavior of tachometer. I happens only while the car is stopping and when
driving in neutral or with clutch down. When it stops, the rpm is fine.

IMG_0278.MOV - YouTube

In the video after speed up to 2000rpm the gas pedal is released.

I had some engine repair before but i can't tell whether it started after repair or it was before (i had my valve seals replaced).