Lid will pop off

I really like this cup and seems like decent quality but the only issue I have with it is that when I put hot coffee in it and close the lid to keep it hot, after a few minutes the lid pops itself off and it won't stay back on unless you have it slid open. I have double checked that the black rubber seal is on correctly and it will still do it. Also, it did not come with care instructions and I'm not sure if it is dishwasher safe and I don't want to risk ruining it.

###

