The most noticeable being the I have had QSLs from LOTW that are two and three years old. Today, I get a new QSL via LOTW from TI5W which was originally confirmed by LOTW back in March of 2012 (4 years ago).
I've seen this several times over the past year since they redid LOTW.
Didn't think you could delete your LOTW log and reenter your QSOs. That's the only way I can see this happening.
I have no idea how this happens or why. Very confusing!
