From your description "Lengthen notes of same pitches only works on notes ... " I assume the 'Edit - MIDI - Lengthen notes of same pitches' path was used.

When clicking the above I get the message in the image below.
I thought you wanted to lengthen the actual individual event if it fits a certain filter/criteria, not combine them if they are close (as described in the image).

This may be working for you because you have notes within a quarter note of each other more often than an eighth, if the message is accurate. Just a guess. Keep us posted on what support says.
Send them this thread.

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