Are you sure that the upgrade itself isn't failing? Could you please go to Luci's overview page and let us know what version is behind the "Firmware Version" field?
There might be a (mt7621 specific?) bug that prevents sysupgrade from working properly. Maybe you are running into the same issue. I am also currently stuck as sysupgrade refuses to update the image.
I had the same issue last week, i fixed it with a second try...
I have had 3 failed flashes in a row now. Anything particular that you did to fix the issue?
You could boot in failsave mode and do a forced flash with
mtd write mir3g-squashfs-kernel1.bin kernel
mtd write mir3g-squashfs-rootfs0.bin ubi
You will loos configuration, so do a backup and restore manually...
Do this on your own risk, in worst case you have to flash the initramfs image with serial in uboot and try again...
Would be interesting whats the reason for this issue.
If you have serial soldered it would be great if you grab a serial log while doing a sysupgrade...
good morning friends
How is the operation of LEDE in the stability of 2.4 and 5ghz frequencies?
I'm using PADAVAN now.
how do I go out and install LEDE? Do I have to go back to STOK again?
I've encountered the same failed sysupgrade issue fixed by flashing kernel1 and rootfs0 manually
Windows command line
for /f %%i in ("openwrt-ramips-mt7621-mir3g-squashfs-kernel1.bin") do ( set /a size = 4194304 - %%~zi >nul ) fsutil file createnew dummy.bin %size% >nul copy /y /b openwrt-ramips-mt7621-mir3g-squashfs-kernel1.bin + /b dummy.bin + /b openwrt-ramips-mt7621-mir3g-squashfs-rootfs0.bin firmware.bin >nul del dummy.bin
Padavan command line :
mtd_write write /tmp/firmware.bin Firmware_Stub
Model : Xiaomi Mi Router 3G
Firmware Version : OpenWrt SNAPSHOT r7043-5df2597 / LuCI Master (git-18.143.80802-59d91d8)
Kernel Version : 4.14.37
I tried flashing by Luci and sysupgrade command a few times each and without success. kernel stays the same version.
That's very weird. It's supposed to be this commit: https://git.openwrt.org/?p=openwrt/openwrt.git;a=commit;h=5df2597c59879029059d09c426dbf10e06c80306
So you seem to be properly upgraded, as that's a commit from today. However, your kernel is still outdated for some reason, even though there was a bump to 4.14.43 yesterday. I'm not sure what's going wrong in your case, as the build does seem to flash.
Another thing is that I don't need to re-install all before upgrade added packages after I do the sysupgrade and because of that I understood that something is wrong.
Then it is definitely not flashing. I had the exact same issue in which packages remained on the system. With a proper flash, all manually installed packages should be gone.
Is there anyone that is running into the same issue and has access to a serial connection? Would love to see if we can pinpoint the reason why flashes are failing. I am having the same issue with my Dir-860L, so more mt7621 devices seem to be affected.
I'm stucked in a version of 4 or 5 days ago too. 
I'm trying sysupgrade via Luci but the version dont change.
I'm in 6952 snapshot and 4.14.41 kernel
Anyone knows how fix this?
As i wrote before, use this method to enforce the partition update...
How?
I tried via ssh and wget:
root@XiaomiMiRouter3G:/tmp# mtd write openwrt-ramips-mt7621-mir3g-squashfs-kernel1.bin kernel1
Could not open mtd device: kernel1
Can't open device for writing!
I think kernel not kernel1
In openwrt
kernel1 = kernel
rootfs0 = ubi
mtd write kernel1.bin kernel
mtd write rottfs0.bin ubi
The flashing issues seem to be caused by hostapd not stopping in time. I haven't tried it myself yet, but you can try killing all hostapd processes and flashing via an Ethernet connection.
Thanks Mushoz.
wrote and ran this over wifi and it solved the problem:
#!/bin/ash
cd /tmp/tmp/
wget https://downloads.openwrt.org/snapshots/targets/ramips/mt7621/openwrt-ramips-mt7621-mir3g-squashfs-sysupgrade.tar
killall -9 hostapd
/sbin/sysupgrade /tmp/tmp/openwrt-ramips-mt7621-mir3g-squashfs-sysupgrade.tar