Quantize pattern , removes note off fromalready quantized notes

I have a pattern where one note lane hase unquantized recorded notes (notice the green delay values )

The others are quantised and have note -offs
When shift+Q ( quantise pattern ) quantize set to value 2 , the note offs are removed from the lane.

Okay , should have isued control + Q ( quantise selection only )

Still a bit odd why note-off are removed with a quant.2 settings