Reverse thrust problem?

Hi people,

Not entirely sure whether this is a problem or simply a realistic feature or quirk, but sometimes when i apply reverse thrust, the engines spool up, and then spool back a little before they spool up to 55%?

It's like the engines "doubt" at 40%, spool down a little, and only then decide to apply full reverse thrust.

Has anyone else seen this?

Note, this is not a controller problem, reverse thrust is assigned to the "Throttle - decrease quickly" command, with the repeat slider full right.