I've had that happen before, and I'm pretty sure I over-tightened the rings. Now I understand what "fingertip" tight means. I did reprocess with new lids because even though they looked sealed, I didn't trust it--same reason I don't buy dented cans of food at the grocery store.

Agree that is the most common cause - too tight bands. Too little headspace and pressure fluctuations during pressure canning can also cause it but by far it is usually too tight bands.

Dave

I was so worried about siphoning that I had DH screw them on extra tight. I guess it backfired. When I checked them this morning, the seal is tight. So do I need to reprocess or is it ok?

Yes, reprocessing it would be very strongly recommended and it must be done within 24 hours. Band tightness has little to do with siphoning. Siphoning has other causes and is applicable only to pressure canning as it is caused by fluctuations in the pressure.

In BWB canning you can get boil-over IF there is insufficient headspace (primary cause) or if the boiling is too vigorous/violent, of if bands are far too loose. But finger-tight is sufficient.

Dave