Just checked and indeed it is not possible to change the step to anything other than 6000. But you can change the start frequency in increments of 1000 so that lets you scan all the 1 Mhz steps by doing 6 scans. I tried that and it picks up nothing on the UHF scan if the start frequency is anything other than the default. But I get a bunch of stations when I scan with the default settings. It looks like you may have a hardware failure in the receiver - the antenna sounds like it's OK since it works with your other receivers. Maybe take the cover off and look for a broken connection? Might be the previous owner did some hardware hacking for whatever reason.