Uhm, thats called a bug. And unless we have your code, we cant help you with that. So we can only give you hints, how to find the reason for it, called debugging. Add logs to your code and check where it goes wrong. If you really wrote the code to delete them, are you sure it really is executed? Happens to often, that you write a new feature and everything looks fine, but it does not work, because you forgot to do the first call. If this does not help, add a breakpoint and check your variables step by step. Maybe they dont get deleted, because you cleared the container to early and lost therefore the reference. Debugging can take some time.

Happy bug hunting!