I'm thinking the predicament is with systems that have multiple/simulcasting sites. The scanners are "hearing" two or more transmitters at the same time, and is having trouble with the bit error rate correction. There is some correcting of this through adjustments, but not enough. It's kind of like there is a "receive echo" that the scanner cannot handle.
Here in Louisville we have such a system. Owing to where I am, the scanner performs really well, or very poorly. It can be just a matter of a couple of yards. I can hear just fine in one place, but move down road 100 yards and the sound is very garbled.
I'm sure Uniden is well aware of this situation - there have been several posts about this over many months. I suspect this is something that the less expensive scanner hardware just can't seem to overcome with respect to an actual system radio which is much more costly than a scanner.
One thing I found is that when I use an older scanner, a 396T versus my newer 396XT, is the problem isn't as severe. I'm sorta thinking as time has gone along, the receive has deteriorated some and, oddly enough, that's an improvement in reception. So perhaps trying to go the route of decreasing the reception, such as through a poor antenna, may be somewhat of a solution.