Well, I dont use that model machine but at 7 inches (although target is usually less than reading) it may be getting to the point of depth where perfect ID is lost. Type of soil matters too. Giving you a reading that is jumping around. This happenens on all machines.
Here is what I would do in your situation and there are a few. If there are really that many objects in the ground ,mostly just dig the shallower ones that ID better ,,and dig every 4th or so ,,target as you describe.(the deeper ones) Pay attention to how the Iffy targets sound and what they turn out to be. If none of the deeper iffy signals are good I would quit digging them after a pouchfull of junk.And depending whats found all together I might find another place to detect. LOL
Also need to ask your self ,what are you trying to find. If you are happy with new coins then just dig the easier shallow targets that ID good. If rings then you have to dig almost every signal. If ur after older coins may have dig all them deeper iffy signals. You know what I mean?
Bottom line is at that deep targets may not come in clear(goes 4 some shallow too), could be 2 or more coins,items , coin could be on edge slightly or some small foil above that is discriminated out ,but causes a iffy signal to target below.
Btw I dig everything for as long as I can take it. depending on what I find makes the difference weather to start getting picky or to go somewhere else.
Good luck