OnePlus 3: Unknown process 99041

If it has no name but just "a number", it's usually some "native" system background process (the number is the "user ID"). You could find out more using adb shell or a terminal app, if you're not afraid of the command line – or using a process monitor app. A good choice here would be OS Monitor, which is available on F-Droid as well as on Google Play:

^{OS Monitor (source: Google Play; click images for larger variants)}

Your candidate would find its equivalent in the process "149" (3rd line from the bottom) in the first screenshot. Being a "native binary", Android cannot find any information in its package list, and thus only gives an ID. First entry in the second screenshot shows what details you can additionally obtain on a process by using OS Monitor.