WiFi Problems (MTK7621A D-Team Newifi D2)

I am having I think a similar problem to the one described here reddit.com/r/openwrt/comments/b3stsx/linksys_wrt1900acs_18061_18062_wifi_is_very/

The WiFI on my router (Newifi D2)
Appears to be much slower and unstable on 18.06.2 then when using 18.06.1
the signal strength for example on 2.4Ghz was much weaker using 18.06.2 and the wifi speed on both was not good.

I have followed this git.openwrt.org/?p=openwrt/openwrt.git;a=commit;h=c0e131b4363dde16a1071131b7e762e36099f780
I have reset the firmware to stock by holding the reset button while powering on, going to the IP and flashing first the Kernel, Restarting, then sysupgrade.bin.
I have tried installing first 18.06.1 then upgrading and first installing 18.06.2.
I have tried remembering settings when upgrading and also forgetting.

I have tried using a development snapshot but didn't appear to work correctly still and the Luci Web interface is very useful.

Is the WiFi issue I am experiencing known? will it be fixed in the 18.06.3 release?
I hope there is a known solution as security is important for things like Routers. Thank you.

Because I am a new user I can't share the links I need to so I am going to include them here but edited so I can post this topic

I would also be happy with installing a different Open Source firmware if it is not simple or possible to fix the latest stable version of OpenWRT for my device.
According to Ebay "Supports variety series firmware, Eg: OpenWRT, ASUSWRT, Tomato, Xiaomi, RippleOS, hi-spider, newifi, etc."
But for example I am not sure what AsusWRT file I need to install for my device though I have been looking.

I found this Xiaomi Wifi Router 3G - 18.06.x / Wifi issues 2.4GHz + 5GHz which is also talking about 18.06.x wifi problems on the Newifi3 D2.
I am going to try installing Padavan at the moment as I found the github for it which seems to be active https://github.com/hanwckf/rt-n56u

The linked Padavan firmware works well so far but I would like to use OpenWRT still if a fix is available, I see this version of the Padavan firmware is unofficial as the official one has not had any updated builds since 2016.
The user who is running this updated Github seems to at least be trust worthy enough for now https://www.right.com.cn/forum/space-uid-179938.html

@Silloon did upgrading to resolve your issues on the D2? What's the performance like on 5GHz? Considering purchasing one.

Sorry for the late reply, I just started using this instead https://github.com/hanwckf/rt-n56u which has been working very well
But I have been thinking I will try OpenWRT again, I am hoping the issues I had have been resolved in the 19 release

I have Newfi D2 and the 5GHz is terrible on 18.06.4->18.06.8 and even on 19.07.2. I haven't tried the earlier versions of 18 just yet.

Any progress one these? I was just about to buy one and then when I looked closely the firmware was not OpenWRT but a port named PandoraBox for MediaTek MT7621 and "Newifi 3". Is that all that will run on it?

I have bought one and recieved it 2 days ago, it has solid hardware and it's price/perofrmance is perfect, but the wifi is strange, mine seem to work fine (speed wise), but while 5ghz can output 20dbm max, 2.4ghz doesen't go past 8dbm, I will be re-flashing the device today and checking to see if that changes, as for firmware, I haven't tested anything besides stock openwrt, but the aliexpress seller that I bought it from had many firmware options.