502 Bad Gateway Errors

Our company just upgraded to AEM 6.4 in July and for the third straight month our site crashed and currently receiving the 502 Bad Gateway error message.  Not sure how to reboot the system from the backend, each time this occurs I have to go request the vendor who developed the site to reboot the program and then the site is fine.  Just getting concerned that this is turning into a broken record.  Are other companies experiencing this issue and if so, what is your remedy to the problem?