First thought: is your tester OK?
Second thought: maybe the Vishays are problematic?
As far as the voltage readings are OK I'd put all my attention to input circuit. Do the tests on one channel to minimize impact from resoldering. Remove the jumper in place of C302. This creates two unconnected circuits: R302, 303, V300 and RCA, switch and two pots. Repeat the measurements across the R302 and the other side of C302 to ground (the volume pot should be at max volume). If the reading across the R302 is zero, then the shorting is directly at the signal side of R302 or input side of R303. If the other reading is zero, then the problem is either in the volume pot or how it is soldered.