According to the date code in the download archive the firmware releases you've tested so far are both quite a bit outdated: 12.0.2.6 dates from october 2016, while 12.0.4.8 ist from april 2018, honestly not worth trying such outdated firmware release at this point. The process over the CLI (be it SSH, Telnet or serial console) is very robust, maybe your are hitting a browser compatibility issue due to your old firmware.
If it's for one switch I'd suggest doing a backup of the config first, then use the CLI over serial console and i.e. copy the latest firmware to the currently inactive firwmare image from a USB key (which is often easier than using SCP or TFTP). M4300's have a RJ45 ("Cisco-style pinoput") or a simple Mini-USB port for serial console. For the later, on Windows you need to install driver from the download section, whereas on Linux no drivers are required. Use any serial console tool like screen, miniterm, PuTTY or Tera Term and connect to the USB-to-serial using 115'000 baud rate.
! Identify your currently active firmware image
show bootvar
[...]
Images currently available on Flash
---- ------------ ------------ ----------------- -----------------
unit image1 image2 current-active next-active
---- ------------ ------------ ----------------- -----------------
1 12.0.X.XX 12.0.Y.Y image2 image2
2 12.0.X.XX 12.0.Y.Y image2 image2
! Copy the firmware image to image1, as image2 is our currently active image
copy usb://m4300v12.0.11.16.stk image1
[...]
! Verify the updated firmware image
show bootvar
[...]
---- ------------ ------------ ----------------- -----------------
unit image1 image2 current-active next-active
---- ------------ ------------ ----------------- -----------------
1 12.0.11.16 12.0.Y.Y image2 image2
2 12.0.11.16 12.0.Y.Y image2 image2
! Activate image1 at next boot
boot system image1
! Verify that this has worked
show bootvar
[...]
---- ------------ ------------ ----------------- -----------------
unit image1 image2 current-active next-active
---- ------------ ------------ ----------------- -----------------
1 12.0.11.16 12.0.Y.Y image2 image1
2 12.0.11.16 12.0.Y.Y image2 image1
! Save current config to NVRAM (precaution)
write memory confirm
! Reboot the switch / stack
reload
After a reboot you can use the CLI i.e. to check the logs (show logging buffered) or the interface status (show interfaces status ...), even the SFP etc. Using the serial console might be it easier to understand as to why your ports didn't come up on mentioned releases.
OK, looks like the firmware update tries to update some sub-components and it encounters a timeout. I don't have an exact idea what PHY8481 means, but PHY in networking oftne stands for PHYsical layer and 8481 could be related to the BCM8481, a 10GBASE-T transceiver from Broadcom, but that's something only Netgear can confirm or deny.
I've had past experiences with PoE daughterboards on M4100's not picking up the its own firmware update after a reboot, but usually after a second reboot. It looks like the newer firmware wants to update this subcomponent and times out. If my guess is right, having issues with some or all ports after the update with these message, seems plausible.
If it doesn't work after a reboot, I'd sincerely suggest contacting Netgear Support and inquire the case there. Maybe it's fixable, maybe there is something off with your switch.
That's where your lifetime warranty on the M4300 becomes valuable, and from past experiences mine were quite good. 🙂
