If it's a glass top, you might double check the seal, though if it was holding empty that's not likely the issue.
One thing I had to do to my humidor was brush a little distilled water on the edges where the lid seals. It held good empty, but when nearly full it would never seem to get up to the right level. I don't know if it was not able to displace enough air to seal when closing when full, but that seemed to do the trick. Keep in mind that your humidor will never have a perfect seal, so environmental humidity will affect it.
Also, keep in mind that the hygrometer measures relative humidity - relative humidity at 70F will be higher than at 75F. Things like Boveda packs will try to maintain constant relative humidity as the temperature increases. Most of my cigars like to be around 65-68%, so I buy the 72% packs during the summer (A/C ranges from 75F-82F depending on time of day) and 68% packs during the winter (heater ranges from 58F-66F depending on time of day). The hygrometer that I recalibrate every 6 months using the salt test fluctuates between 65% and 70%. To make it easy to verify that I'm still within range at a glance, I "clock" the gauge so that 67% is at 12 o'clock (you know, like you might put your low corner RPM on your tach in an oval track car, or shift RPM if doing drag or a lot of shifting).
One thing I had to do to my humidor was brush a little distilled water on the edges where the lid seals. It held good empty, but when nearly full it would never seem to get up to the right level. I don't know if it was not able to displace enough air to seal when closing when full, but that seemed to do the trick. Keep in mind that your humidor will never have a perfect seal, so environmental humidity will affect it.
Also, keep in mind that the hygrometer measures relative humidity - relative humidity at 70F will be higher than at 75F. Things like Boveda packs will try to maintain constant relative humidity as the temperature increases. Most of my cigars like to be around 65-68%, so I buy the 72% packs during the summer (A/C ranges from 75F-82F depending on time of day) and 68% packs during the winter (heater ranges from 58F-66F depending on time of day). The hygrometer that I recalibrate every 6 months using the salt test fluctuates between 65% and 70%. To make it easy to verify that I'm still within range at a glance, I "clock" the gauge so that 67% is at 12 o'clock (you know, like you might put your low corner RPM on your tach in an oval track car, or shift RPM if doing drag or a lot of shifting).
