Is a cleanout needed?

I got a letter from the water department saying we used 28k gallons last month instead of the usual 3k around the same time last year. They came out and looked. I shut of the water in the basement, turned on the sink, no water. They said the meter was still running. So now I have to dig up the lawn and find the leak. I'm too busy to deal with it for the next few days so I filled up a cooler for washing hands and such and shut the water off at the meter. It was reading 0.4 GPM when I shut it off. A while later I turned it back on for a minute to use the bathroom. I went to turn it back off and when I did it was at 0 GPM, occasionally going to 0.1 GPM. I had my wife turn on the tub and it went to 4 GPM. She turned it off at it stayed at 0 GPM. Also, no evidence of leak in the lawn anywhere. No soggy ground or anything. It's a digital meter. There is a tiny device and what looks to be an ethernet cable. It seems to me that instead of a leak, the meter might be faulty. I will call the water department Monday and see what they say and if they can replace the meter. I think that occasionally, after water is no longer flowing, the meter will get stuck in the open position, registering water is still flowing. Flowing water again might knock it back so that it closes again. That is my guess but I wanted to see what someone with more expertise might think. If so, it sure beats digging up my lawn.

We have a modular home was plumbed with all pex and CPVC. I have a problem losing water pressure when you turn one thing on that flows a lot you lose water pressure the whole rest of the house. I put a pressure gauge in where the water comes in from the road and when you turned something on I would only get about a 5 psi drop. I went out to wear the garden hose hooks in and opened up the same valve and I got like a 20 psi drop. Any idea of how I can go through and figure out where my restriction is. On city water with no pressure regulator. It's a very small town. I have about 60 psi coming in.