My Virus b has NO Sound and some other problems after OS Update.

Hi everyone, I would like to share my experience with you and maybe get a little help if possible, in case you have experienced ANY of the following, as a last try for me before I send my “Virus b desktop” to service.
About a year ago I bought a second hand Virus b, with it's manual and everything in perfect condition. I actually went to the house of the guy that sold it to me, and took it like a baby back home. I tested it in his house and then back to my home studio for a couple of days and everything was working perfect.
Then I thought of updating it's OS to the latest version (Virus B Series OS 4.90 Build 050 English). I used Nuendo for this, on a well setup pc computer with all settings related to sysex filtering correct etc. The Unit got updated fine without any errors and rebooted itself. All great and fine. For some reason I had to place it in a better point on the table so I turned it off. So here comes the weird part. After turning it on there was no sound. I searched on google and found that happened to others too and all I had to do was to power it up by holding the SHAPE button in order for it to reset itself. So I did, and the sound came back. But sometimes till even today, when I turn it on there is no sound, and actually, turning it on with the SHAPE button pressed does not always bring the sound back. It is even not a mater of being warm or cold, it just happens not to have sound, and other times to turn it on, and have.
Some more facts, the update I used was the right one for the unit (in my case the “S”), it does have midi activity (using a motu 828 mkii firewire), I can see the little note (filled head) on Virus on the same channel I play from the external keyboard and on Nuendo (channel 1), even tried all different outputs. I also re-sent the OS update more than 10 times using different methods such as midiox, cubase, media player, even from my laptop computer, even tried different bpm like down to 80. I also tried going back and sending all the older OS updates I could find on the internet, re-downloaded the latest in case the file was corrupt. I tried different cables of all kinds including power supply from a friend's working Virus. I also changed it's battery 2 times just in case. The Unit's inside looks absolutely clean and in perfect condition.
So as a temporary solution (until I take it to service) is to use sysex for the songs (as I would anyway) and bring the Virus in the condition it was before saving the song, once, reseting it every time I power it on, it loses everything. The machine works perfect as if it has absolutely no problem (when it has sound right?). But a weird thing is the following. After I send sysex to Virus (global, arrangement, singlebuffer) of a song I load on Nuendo, although Virus receives them without error messages, the EFFECTS of each sound have the COLOR setting “forgotten” in a way, although I can see it being set to say “DELAY (MULTI) Color -45”, it doesn't sound as if it's set to that. As a result that can be missing DELAYs from a patch etc. Only if I turn that number to “-44” (or any other) and back to “-45” I can hear the DELAYs, as if I “wake Virus up”. That happens ONLY right after the Virus will receive that sysex from a Nunedo song, if I keep it on for hours or days it will not have absolutely any problem with anything. But as a test, if I re-send that sysex or any other at any moment, then Virus will go to that state I just described. Anyone of you ever had such an issue with a good working Virus b or other ? Weird stuff...
As a result, I just think that having the brilliant idea to update it, I killed it.
I have contacted the tech support, which was great, but they couldn't help me any further and told me to send it to service. I also could not find any diagnostic tool. But I would very much appreciate if you could share any similar experience or any ideas maybe really.
Thanks very much!

thank you indeed for the reply,
do you really think that this sounds like an issue that can be solved without taking the unit to service ?
I am really sad about all this