I installed v2.1.40 over the weekend, and played (or tried to play) a couple mkv movies. The first one was 4k/HDR and it had lots of loud audio pops. The audio track was DTS-HD Master Audio 6-channel. The video was HEVC x265 - 10bit Main 10@L5.1@High, frame rate 23.976. I couldn't even watch it - I quite after a few minutes. The video didn't stutter and no dropped video frames, but the audio would suddenly have a loud pop. I then played the file plugged directly into my TV using it's built-in media player, and it played flawlessly with no audio issues. So the file is fine. My PC plays it fine too. The second file was a 1080p blu-ray remux (23.976), and about 2/3 of the way through, the frame rate suddenly turned into a stutterfest, looking like a stop-motion film. At first I thought it was the film using a fancy slow-motion/stutter effect as it happened during a dramatic part, but then I paused it and then un-paused it and it played normally for the rest of the movie. Checking the scene again afterwards it was not the film, but the player as it played fine when I checked that scene again. I've had tons of issues with audio dropouts and loud audio pops with this player, since I bought it way back, but the stutter issue with the blu-ray remux is unusual and I haven't seen it before this latest firmware. Usually when I have audio drops or loud audio pops, the video plays fine - no dropped frames or stuttering - the audio just seems to glitch out. I keep hoping another update will fix the audio drops/pops but it never does. Sometimes files play through fine all the way, and sometimes it's fine until part-way through, and sometimes it's a problem right from the beginning. I play the files using a USB 3.0 thumb drive plugged into the player using Media Center from the home page, not Home Theatre.
Don't know if I was lucky but after a mkv riddled with this I ran task killer + cache cleaner, & the next played pop free.
