What would make an acrylic fish tank leak intermittently?

I have a small acrylic fish tank (called a Mini Bow), one gallon, on my bedside table. About a month ago it was leaking slightly. I wiped up the water and it did not leak again. Then about two weeks ago, I was on vacation, came home to find water all over the floor and the tank about half full. I took the tank, changed the filter and inspected it all, and put it in the kitchen sink for a day. No leak. I then moved it to the kitchen counter for 4 more days, on a paper towel. Dry paper towel for the duration. I then moved it back to the bedside table. Last night my daughter noticed it leaking again. I had to clean up the water and then I put it on an enamel tray with a lip. This morning there is about ¼ inch of water on the tray, and the water in the tank is about an inch lower than it was last night.

I have no problem getting a new one and I will have to get a new one, but I am just curious why it would not be leaking every day. I don’t want to get a new one if it’s something that I should be doing or looking for.