I just received my 536hp, monitoring the winston/Forsyth co. Motorola smart zone system with apco 25 voice. I picked the best manual threshold level at 11. I still get error rates around 20s and 30s. Updated to latest firmware. I can't get the error rates lower. Although the voice reception is fine, every so often I get the motorboating noise for a second or two. Might happen twice an hour. I can't match it to any particular talkgroup. No group appears when it happens. My 996xt does not do this. Signal strength is full bars. Any ideas of a setting that might help? Thanks. I switched from nfm to fm decode with no effect. Also changed modulation from auto to fm and nfm with no change.