I know I am not the only one with this problem. I also know this problem is apparently beyond the scope of Uniden's ability to fix. Nevertheless, I'll add my voice to the issue. I am unable to hear the beginnings of ANY P25 transmissions. Analog is fine. Additionally, sometimes in the midst of a transmission the voice clips as if the transmitter were over deviating. I've been using fixed frequency (crystals) receivers and crystal controlled scanners since the '70's. I really wish Uniden et al would take this seriously enough to DO SOMETHING. At least before everything switches to TETRA.
This seems to be the rule rather than the exception, based on my experience with two each of the SDS100 and SDS200 that I have. And DMR appears even more unreliable than P25 on the SDS series, with not only drop-outs and "clips", but volume fluctuations which go from barely audible to blasting on the same systems from transmission to transmission. The AOR DV1, at twice the price, is slightly more reliable, albeit without all the scanning functions of the Uniden series.
Realistically (no pun on Radio Shack, for the old-timers), this seems to be pretty much state of the art when it comes to a "scanner" in the $700 USD price range. You might get slightly better P25 on an Icom 8600, but at $2500 - $3000 USD, you would expect that. And it sure as hell ain't "portable".
I continue to be amazed that at the SDS price range, Uniden can offer as much as they do. Sadly, with the untimely death of Uniden's Paul Opitz, I think that the impetus to improve on the current SDS series is also gone. You can see that there have been no firmware updates for quite a while.