The new cable (V2) just avoids this by not using pin 4. It means we have 1 less pin for data which should in theory reduce the maximum bandwidth, but I was able to optimise it quite well and didn't loose much performance.
Newer style VecLink Cable
Vectrex A Vectrex B
1 |--------------------------| 1
2 |--------------------------| 2
3 |--------------------------| 3
8 |--------------------------| 8
All other pins MUST NOT be connected.
(or damage to your Vectrexes is quite probable).