Seems to be defective. I have two - one holds the vacuum forever and the other loses the vacuum completely after 1-2. I should actually exchange one of them.

It's the same for me and another person I know. Tightening it very firmly helps it to last longer. I think this has to do with the sealing ring, which is not compressed enough if you don't tighten it like a berserker. But it's a fail on the part of the product.

It shouldn’t be normal but, unfortunately, I had the same problem. After just a couple of days of usage, the vacuum was not holding for more than a few hours. I’m very disappointed - will return it!

I bought 2 and registered one as defective
The vacuum lasts 1-2 days on mine and then it's over
Because I make coffee every day, it works - but I can't recommend it for longer vacuum guarantees

No worries on my side, the vacuum has always been excellent even after more than a year of use. It looks like a default product.