Unexpected delay while inputting notes

wether or not I do this with the mouse or MIDI keyboard, I noticed this strange delay:
at bar nr. 150 onwards - this may be not of any significance - every first note of a new bar [while inputting] shows some delay, all other notes in that bar don't.
On bars without divisi or with only one voice this doesn't happen.
Raymond
- on all staffs where two or more voices are once input - non-strings staffs
on all staffs where for strings once a divisi, so two voices, was introduced somewhere
at bar nr. 150 onwards - this may be not of any significance - every first note of a new bar [while inputting] shows some delay, all other notes in that bar don't.
On bars without divisi or with only one voice this doesn't happen.
Raymond