I tend to agree, but have you tried the trick of placing your "spare" hand flat on the wall a foot or two to the side of where you are scanning ? That can improve the performance of the cheap Bosch detectors sometimes.
There has been previous discussion on the forum about the very expensive Bosch versions with Lidar technology being used for critical drilling in concrete between embedded services, rebar and whatnot. Apparently excellent but very expensive devices.
Use the search function and you will find some relevant threads.