I'm sure it is functioning as it should since, as mentioned, the Silver Sabre microMAX uses the ED-120 Discrimination circuitry design, and that means a minimum Disc. setting will reject most nails and almost most iron. The exceptions for the Tesoro's or any detector are the problem targets of man-made ferrous material such as washers, rusty tin, bottle caps, etc. There are ways to help audibly classify those, however.
The secret/tip for success using any of the preset GB model detectors is to select one preferred search coil, such as the 6" Concentric I keep mounted on mine, and then tweak the internal GB trimmer so that you have a best-functional GB setting for the Discriminate mode. It's best to do that in some of the more mineralized environments you might hunt, and that will include the gold mining era ghost town sites we will be searching this coming Thursday thru Sunday on our 6th Welcome-to-Hunt Outing here in Eastern Oregon. I'll be glad to check your unit out so we can ensure it is functioning properly. See you later this week!
Monte