PA0PBZ,
Are you able to measure the actual input impedance of the V2.0 hardware in 50 ohm mode, using a VNA or some other suitable tool, please?
The original input is 1M || 16pF, and if they just slapped the 50 ohm across the input, then the 16 pF may still be there. That would create a rather wonky impedance mismatch above 50 MHz or so, not good in many situations.