Amiga 3000 - 7 LED Flashes and Reboot - bad Cyberstorm?

[Whaka]

Glad I don't have a MK3, then

it's not a so common fault because of the design.
usually this happen because of extraction of the cpu. this require a special extractor to not apply force on the socket. with screwdrivers... you have to be really careful.
or if you really badly bent the pcb

[Whaka]

i said usually. of course, everything can simply fail...  
i have an mk3 too, the socket failed because i did multiple extractions. i fixed it the same way as Acill describe, near 10 years now.
 
and cpld are running really hot on those cards, this doesn't help.