P.S. I'm referring to toiletry containers

Interesting & I'm not sure the answer. I have never experience that. And I always use 1 or 2 oz. plastic bottles that I put my own stuff into. And sometimes purchased travel-sized like lotion. Never had one stuck closed after a flight though.

get containers you can screw and unscrew during the flight

pressure changes go from sea level to 7500 ft of pressure

quickly causing sealed containers to expand/lock sometimes

Also Causes "BaroTrauma" ear and sinus "squeezes" can really

hurt sometimes from personal experience...

My containers are in my checked luggage. No way I can be opening and closing them during a flight!

Were these hard/rigid plastic? Mine are soft/squishable type plastic.

I only do carry on and have used MANY travel containers over the years. Never once have I had to unscrew/screw them mid-flight -- and never once have I had one seal itself shut, let alone 'some'.

What products were in them and what sort of containers were they??

I've never had that happen. I am currently using what I thought were called Goo Tubes, but I now know are actually called GoTubes.

("Goo Tubes" turned up some interesting search results on Google. If you don't hear from me on Fodor's for a while it's because I'm too busy looking for a new job after being fired by my current employer for inappropriate use of a work computer to access porn.)

Use a funnel to make sure none of the product gets on the thread of the container. Use flexible containers that don't leak air or product.
The problem I usually have is sealing a container at a low elevation (high pressure) and opening at a high elevation and getting sprayed.

Wrap a rubberband around the lid and twist. It works like one of those jar grippers. It also works great for soda bottles when those tighten up randomly during the day.

Any hotel desk should likely have a rubberband or two that you could borrow or have.

I have a couple of tiny hard plastic jars that do this on a regular basis and the rubberband works like a charm.