Does that radio use a dynamotor? The boost regulator may not be able to handle the startup surge.
The vendor has a warning about high current stresses at low battery voltage damaging the "power tube" ! Funny!
However the driver(s) will need to sink quite a bit of current at low voltages and I suspect this design may be at the upper edge of the part's specification.
When it blows up , they'll say "we waned you".
RFI may be an issue too.