They might be right about the memory leak. Any server monitoring to observe with? You should be able to tell pretty quick.
Also, review any Custom SQL Queries or reports you have running or scheduled to make sure they aren't looping, and creating an endless query (or a temp table too massive for your system to handle).
short of suggestion you upgrade? I'd start by moving the SQLserver to the latest version supported by the version of NPM/NCM you are running as that is the least painful
I will have to go in the SQL and check queries; I am not sure they are keeping up with reports and schedules. I believe they are using out of the box utilities. But I will look for endless queries.
Eventually, we will move to a new SQL upgrade and server but we have to wait for upper management approval and funds.