ProCurve 3500yl: All LEDs blinking after Software upgrade and loss of network connectivity

[NullDevice23]

Hello,

We have several Procurve 3500yl (J8692A) switches here.
They all had software version 11.x, which is pretty old.
I upgraded 3 of them some time ago to the current version.
Now i also upgraded that last one of those 4, and ran into a problem.

The recommended steps are: upgrade to K.12.62, from there upgrade to K.13.68, and finally to K.15.13
I did it exactly like i did with the other switches: per TFTP.
I reset the swtich first to factory defaults.

In version 12.62 everything was still absolutely fine. But after booting into 13.68 the switch was behaving strange:
Like every 30 seconds all Port-LEDs and other lights are starting to blink. As if it was reset.  During that, you can still execute any command in the serial console.  Just only the network connectivity is lost.  When its finished, network connectivity is back to normal. But after like 30 seconds its coming again and again.

When i boot the other image on the flash, which is 12.62, everything is fine.
Back to 13.68 : same problem again.
I also tried to reset the config again to factory defaults, but the problem is still there.

What could that be? - Any ideas?

Thx in advance,
ND.

[Vince-Whirlwind]

Anything in the switch log?