House has sump pump & ejector pump. Only connection to ejector pump is water softener (no basement bathroom). Ejector pump runs routinely, but sump pump very rarely runs. City water department tested recently, advised that we have a leak into the pit (did not open pit, though) and mentioned something about a possible bad flange(?).

I know nothing about these systems...
Is there some sort of "flange" that could be the cause of such a leak into the pit? (House is 14 yrs old, neighbors say that builder likely punched holes on the pit to keep foundation dry during construction & left it that way.)

If I were to unscrew the lid & open it up, will the lid still be safely secured after I screw it back down, or is there some of seal that I'd be breaking if I were to do so?

Thanks for wahtever advice you can give!