Try checking the minidlna log see any hints or if there’s any media fail to index which can cause it to retry scanning everytime.
You could also off the inotify in the conf but it will need manual scan when new media added. Your idea of cronjob is quite acceptable but yes it’s not a proper solution.
Sorry I can’t test this further. As you would have know, I’m running this installer off my wdmycloud (nginx+fastcgi), also several other sites so it hardly sleeps.
