I've described the video bug with screenshots here:
https://xiaomi.eu/community/threads/7-10-19.41961/page-19#post-391780
It's basically a video resolution upscaling issue that happens within apps such as YouTube. Many official bugreports were sent to Xiaomi itself, but a fix is still pending. Only weekly builds from 7.7.20 onwards are suffering from such glitch (actually even the latest stable 8.5.5.0 suffers from it, but xiaomi.eu team has not released it as they're working hard on MIUI 9).
I'm personally running the weekly builds as I'm not using any of the affected apps, and MIUI 9 is way better than 8. There are still few minor issues, but we're getting colser to a first stable release. Anyway it depends on what is your usage. If can deal with possible bugs and handle them, go with weekly. Otherwise if you prefer a more stable but older build (and you're using those apps suffering from the "zoomed vdeo issue") go with 8.5.4.0 then.
If You dont report bugs in Official forum miui.com (china forum) or dont click button "confirm" in already existing thread with bugs on Mi5C, than all issued on this phone not will be fixed. You can also try same create bugs thread and click "confirm" on official international forum en.miui.com).
Yours report bug on Xiaomi.eu forum its
not give any results, because it phone typically to the Chinese market for network China Mobile TD-LTE, if the Chinese does not improve, here also no one will do. If You have any problems with the modem (Internet access mobile, range) is it codes USSD, just as of zooming in the application FB, YT or with fc in check-version in code 6484 in english language.
In China Mobile TD-LTE not have problem with range, mobile internet, not have problem with ussd code. On china language in China rom not FC in Check version on 6484 code. They dont use GAPPS officialy(They have Mi App Market) and They dont know about bug with zooming on apps like FB and YT from Gapps. In China in Unicom Mobile have simmilar problem with range and mobile internet.
Mi5c not support B20 FDD-LTE(Unicom), not support 4G+, officialy suport volte only in China, officialy full bands support only TD-LTE, our FDD support only after set 5 mode in song Assistant but only bands 4G FDD-LTE B1/3/7.. Officialy full suport only 2G in our Region.
If You want help and solved problems,bugs anf issued in MI5C report bugs or click confrim on existing threads on this sites:
Official China Forum(recommended report bugs for MI5C)
http://www.miui.com/forum.php?mod=bugfeedback&fid=16&page=1
And
Official Internationa forum (additional place)
http://en.miui.com/forum.php?mod=bu...ons=&rom_version=®ion=&sortid=1&con=&pid=0
