Strange cluster backlight and voltage issue

I have 2007 volvo 670 isx. The cluster blacklight goes out and comes back one again suddenly or when there is bump on the road. Also when that happens I see the voltage goes to 24.0 v. Sometimes not always. Also this only happens when truck is cold. Once it's been running on the road its normal.
Sometimes when the backlight is out. I hit the dashboard it comes on.

Yesterday I opened all dashboard and fuse box kept moving wires with engine on. Nothin happened everything was normal. After 2 hrs search I put everything back again.

I checked all connections on battery too seems to be ok. Problem seems to be with ground wire. What should I look for.

 

Everything else is fine it's just these two issues I have seen. Everything else works fine. Even the cluster display work and all gauges work. Just the backlight goes dark. I will check on those fuse. I know it something to do with wiring. Cause I was driving thru 60 km wind gust and this started happening. The batteries doesn't not charge to 24v. Cause I stopped the truck and restart they were back at 14.3v