My glass stopper got stuck in the test tube

This is a recurring issue I encounter when utilizing glass stoppers, which led me to switch to plastic alternatives. However, I was unable to find stoppers of the appropriate size for the test tube I am currently using. Could you please offer some guidance on how to prevent this problem? I have attempted freezing the entire tube, and while there is a small amount of gas visible in the neck, it has not released.

It's crazy this kind of things are still unresolved for me, even after I use everything I know from this sub