Even without a variable background sensitivity, detection rate should be related to hours of darkness - i.e. hours of observation.

There may also be some other effects, such as that in summer the scope is north pointed at night, and the northern hemishere has been better examined so has fewer new finds than the southern hemishere or equatorial belt

(of space, not Earth - I find I lack the nomenclature to describe these things accurately. We are tsalking about the plane of the ecliptic, methinks, and whatever is north and south of that).

Here's where a contact on the observing team would help us understand the limitations and constraints.