The bug about the panic mode is in the issue tracker https://bugs.openwrt.org/index.php?do=details&task_id=1650 but i don't know if it should be useful to post bugs about the "reboot cycle" and the possibility to change something to make possible a successfull factory reset using the router buttons, or making not available the 5Ghz mode with the open source driver in the main releases (for example, with the Huawei HG556a needs to install a driver to use the N mode, the open source can use it, and that info is in the wiki).
Everything of this happens with the lastest release, 19.07.1.
This is for consult how and what add about all this info to the wiki, and later made some research and tests about if there is any possibility to make this router work again without using any hardware option (doubtfully).
PD.: As pointed here Links limit for new users i have edited all links with extra spaces because as new user i only can post two links. Sorry for that.
If all you did was enable the 5ghz, you should be able to grab this tool(if you run windows), and set your ethernet adapter for 192.168.1.2 and your gateway to 192.168.1.1, browse to the correct firmware, and click upgrade at the same instant, or a second after you power on your router.
I use the E3000 for my home network, but its been a while since I bricked mine, so that's the procedure from what I recall. The red, green, and black wires coiled up on top in the picture are soldered to the serial pads on the board, so I always could see when the router was ready for me to start the tftp the two or three times I bricked it over the years. There are also serial pads in the WAN port, but I never tried to use them. I have seen a thread about someone using them
In any case, I now use a separate wireless AC access point, so can't help you in that area... haven't even tried wifi with openwrt, but it did work with freshtomato FYI
That's something i was thinking until this morning, when i do continuous pings to the router with 192.168.99.x manually configured in the PC meanwhile it is in the "reboot cycle" and i have some pings back. But with 192.168.1.x i have one ping back too, so the problem here is i lack the knowledge and tools to make a proper testing of what are happening here (that's what i will try to do), but now i don't think is really reset, because i manually put that 192.168.99.x IP range.
Now i can't reproduce this, but i think it's i putting Windows crazy with all these connection reboots.
I did in the past some wiki editing in other sites, but as a new user and limited openwrt experience i need to ask first if i can do it or it's better some one else do it, because i'm not sure what templates you use, and what to write. In my opinion the two things i think are important to know are the problem with using 5Ghz with the default driver and the lack of an emergency reset. I think i can do it, but i need some advice.
I can't do it, first, because it's in a "reboot cycle" when i only switch on the router, it reboots in 5-10 seconds losing connection every time.
Holding the WPS button, and using the reset button (some links above talk about these methods) i can make the router holds on and it does not reboot, like be in a recovery mode, but i tried to reach with all IP ranges without any luck (in fact, one link said it use DHCP and i don't need to manually put the IP, but when i do that appears the mentioned 169.254.234.71 which seems it's Windows putting an IP because DHCP is not working).
I tried some factory reset methods too, but anyone change anything of the behaviour. When i installed OpenWRT it works, and it switch on perfectly and i was using it until i tried configured the 5Ghz antenna (which is the main thing about this topic, to warn people about this in the wiki)
If you were to solder leads inside, or modify something for holding leads onto the serial connection inside the wan port and attach a serial adapter of some kind, Ill bet you would see a 1-2 second prompt to begin uploading the firmware as soon as you power it on. Worth a try maybe if you need to revive a low power router for s and giggles
I know i'm bumping this old topic again, but i want to post about the last week i brought back to life this Cisco Linksys E3000 with the short circuit method. It's dangerous but it worked and it was very easy to do.
Now i know it works, if there is no issue i could add some info about this in the Wiki. I'm not going to point to the "short circuit method", but to this topic, and maybe a warning to not configure the 5Ghz antenna or doing it knowing the risks. If that is okay.