I don't know how the sweeper works, but with close call on my sds100, I think it measures the rssi level. So it has to be over a certain number for the scanner to both looking for it.
If you have a target or walmart, mall near you, sit in the parking lot and see if that works. If it doesn't, then something is wrong. I know my trx1 scans super close compared to my sds100 but I still get 90% of the same hits on the trx as the sds. I don't use OEM antennas though. The stock one on my trx is horrible.
Remove the antenna from the scanner and set squelch to 0 and increase until the squelch closes and then add one extra notch. Look at how fast the sweeper goes over the frequency ranges. Then connect the antenna and check if it slows down. It could hesitate a few times but not slow down in search rate for longer than a second or you have too much interference that knocks out the sweeper function. I have to use a variable attenuator at the antenna port and slowly increase the attenuation until it stops to hesitate. That's the sweat spot where it works the best. In VHF I need to use an external FM broadcast filter to be able to use sweeper.