Right channel has no output in high impedance mode

[N72826]

Just finished the final voltage check, everything was solid so I did a listening test and found I have no output in the right channel when high impedance is selected.

I know the recommended advice would be to reheat every joint but in the hopes of not having to do every single one, is there somewhere I should start first given that this issue only affects the high impedance mode?

[Thermioniclife]

I think I would resolder the imp. switch joints and if it still does not work check for the proper connections to the output transformer on the offending side. There's a possibility that there may be a broken wire connected to the trans or switch. Just one old mans opinion.