Alright, I'm giving this one last go before I throw in the towel and just live with it.
I've had an ongoing issue when trying to operate an XTS5000 on a duplex analog VHF system for work. No encryption, no digital, just old school FM. The channel I'm trying to operate uses DCS squelch #263. Every 10th or so transmission, it cuts "in and out," and occasionally doesn't play at all. The red LED indicator light is flashing, though, so I know that the carrier squelch is still picking up the transmission. The cutting in and out never starts in the middle of a transmission, though. Either the entire transmission is perfectly fine, the entire transmission cuts in and out, or the entire transmission doesn't break DCS squelch.
This problem has been replicated with two separate XTS5000s, both tuned and aligned.
I've found that the only fix to this problem is removing DCS squelch. If I only use carrier squelch, all the audio comes through loud and clear. None of the other settings in CPS have any effect--MDC signaling, squelch muting (I wouldn't expect this to have an effect on DPL squelch anyway), ultra narrow intermediate freq filter, and squelch fine tune. The channel operates on 12.5 kHz spacing, which is correctly programmed.
This problem happens regardless of proximity to the repeater. Additionally, this doesn't happen when I tune in to other channels using DCS squelch--on the contrary, everything works perfectly. The radio has been recently (<1 month) tuned and aligned on a service monitor. None of the mobile or (rare) portable radios used by the company have ever had this issue. FWIW, all of the other radios on both the working channels and the problematic channel are Taits and Kenwoods, not Motorolas.
Now this wouldn't be a problem if the repeater didn't send out an obnoxious sounding DCS cutoff code at the end of every transmission, which means listening to the channel with just carrier squelch makes me want to rip my hair out. But given that I don't have a ton of other options and I don't have the time to troubleshoot this for all of eternity, I want to see if there are any other opinions or suggestions out there before I raise the white flag. My last guess would be that the radio is misinterpreting a cutoff code, but I otherwise have no idea what's going on. If anyone has any ideas at all, please let me know!