ubuntu 20.04 virtualmin mysql turns off after sometime

hi, i install virtualmin on a fresh ubuntu system. everything works fine. except for mysql. it goes down after 30 min. and even if i restart it. it goes down again after sometime. i reinstalled everything. even i started a fresh install. the same issue is showing. and i tired many things. still it is not working as it should.
only people with experience in the subject. will be accepted. thank you.

Good Luck to all.