[Dxbase] Strange LoTW QSL behavior

[Ed K1EP]

I periodically use the Selection Wizard to create an ADIF file which I then submit to the LOTW.  When you do this, there is a window that asks if you want to flag those QSOs as being sent to the LoTW.  Back in January, I created an ADIF file for a 10 day period between January 20 and 30 and checked that I wanted those QSOs flagged.  It had over 700 QSOs in it that I submitted to LoTW.  However, only about 60% of those QSOs got flagged as being submitted.  As I scan through the log, some of which took place during the CQWW 160M contest, I see some QSOs on Jan 28 being flagged and others not.  Not so for the contest QSOs on Jan 29.  All of them are flagged.  I can't seem to correlate anything as to why certain QSOs were flagged and others not.   Has anyone seen such behavior before?