+ AA6YQ comments below
It is very frustrating to see that in LOTW there are 2 qsos with the same call, mode, freq etc. BUT the time is sometimes 30 to 45 seconds difference.
+ That's not what the message ""no matching QSO in log" means, Patrick.
+ For example, if you submit a QSO logged in DXKeeper with a start time of 9:24:31 to LoTW, then change the logged QSO's time to 09:24:00, and then invoke DXKeeper's "Sync LoTW QSOs" operation, the result will be "no matching QSO in log" -- because there is no QSO in your log with a start time of 09:24:31.
+ The actions of your QSO partner cannot cause this error message; it can only be caused by your actions, or by an error in LoTW.