Please check all Traces & VIAs in marked Area's!
Often there are Problem's - renew Solder Blob's!
On Top of the PCB the VIAs (
Vertical
Interconnect
Access) looks like they are ok; on Bottom Side -> the SAME VIA have a failure Signal, or they are broken.
Example:
It's a A600 without "Red" - at this Point -> the Line would be broken at the Pad! Similar to your Amiga -> look ath the VIAs and - i hope so - connected Traces