OK this is probably going to be a bit of a long post and if I have posted in an inappropriate thread Admins please feel free to move it ... Hope this helps those with similar issues ...
Please keep in mind these setting changes worked for me on my box with my TV, internet connection and network so YMMV ...
For starters I have a M10 MXQ S812 METAL TV BOX running Android 4.4.2, Kodi 16.1 w/ IPTV66 and a Real-Debrid subscription, which has been experiencing a lot of buffering issues as of late for some reason. I'm also using IPTV Stalker Plus Lite w/ the PVR Stalker Client. Since I use this box as my primary TV source I was extremely frustrated by this and decided to try and limit the buffering if not eliminate it. Like many many others searching this forum and the internet I have used the Easy Advanced Settings tool and made changes to various settings that seemed to work for a period of time and then would start acting up. I continued to adjust settings and numbers (posted below) and again it seemed stable for a while and then would start acting up. So I decided to make some rather radical changes to my setup including changing the Display Output on my box from Auto-Detect to 1080p @ 24 Hz and setting up QoS rules on the routers on my network. Since I've made these changes buffering has virtually been eliminated and streaming from both US and UK channels has greatly improved. The changes I made are outlined below:
Changed Display Setting from Auto-Detect to 1080p @ 24 Hz
Setup QoS rules for LAN Port and MAC Address w/ Highest Priority
Manually set DNS to Google DNS servers (220.127.116.11 and 18.104.22.168)
Easy Advanced Settings:
Network BufferMode: 3
Network CacheMemBufferSize: 346030080 (330MB or 1/3 of Kodi's reported Available Free Memory)
Network CurlClientTimeout: 30
Network CurllowSpeedTime: 30
Network ReadBufferFactor: 90
PVR CacheInDVDPlayer: True
PVR MaxVideoCacheLevel: 180
PVR MinVideoCacheLevel: 180
Now I know I committed a "mortal sin" by setting the Buffer Mode to 3 as reported by many many others however when setting it to 2 or even 1 the buffering issues continued. I assumed however for those running older IDE or SATA drives this could be an issue as wear and tear on the read/write heads and platters could reduce drive lifespan but my box uses a MicroSD card which is essentially a Solid State Drive more or less (no moving parts, no wear and tear) so making this change didn't bother or phase me as a setting that would "ruin" my box or limit its lifespan. I also know some of these settings seem "high" or unusual to many but like I said earlier these changes seem to work best for me and has extremely limited my buffering issues and streaming is a lot lot smoother and enjoyable than it ever was prior to making these changes.
I hope this helps anyone, particularly newbs, experiencing issues w/ their box. Hope everyone has a Happy New Year as well ... Cheers!
PS - Don't be "afraid" to experiment and find the setting(s) that work best for your setup.
PPS - If anyone has an updated firmware (Android 5 or 6) for my box I would greatly appreciate a link or any info as to where I can download it as I'd like to be able to eventually run Kodi 17 (which reportedly only runs on Android 5 or better) w/o having to buy a new(er) box. Thanks in advance!