RPM too high shotening run time

I purchased the mower last year and all was well.  This year during the third time mowing there was an incident where my tire slipped off the grass edge into the garden causing the deck height to drop and bogged the mower down for a second.  Once recovered from the bog-down, the RPM was instantly higher.  I thought initially that it sensed the need for more power and entered a turbo mode.  However, the RPM never returned to normal even after future uses and charge cycles.  This is a problem since it drastically shortened run time which before was 40+ minutes dropping down to 22 minutes at best.

See the video for a side by side comparison of the old and new mowers.

I contacted customer support and was told they had never heard of this condition.  They sent me a new mower and charger (sans a new battery).  I was able to compare the two mowers using the same battery and the new mower very clearly runs at a slower RPM and it's cutting and run time performance is as it should be.

I could not find anyone else claiming to have this experience but perhaps it is happening to others and they are not really noticing the RPM difference.  I do see where folks are having trouble with run time being shortened though so maybe the higher RPM issue could be the cause in some cases.  It certainly was in mine.