[Arran]

I had forgotten about that, Canadian Westinghouse used to like encasing audio coupling caps inside of a metal shield screwed to the chassis, they also liked to use shielded cable to connect them, and the volume control. It is easy to miss them during a bulk recap, someone did this in my Westinghouse 780A, twice!!
One way to spot if the volume control was a replacement is if the shaft of the control is noticeably different, most of the others will be made out of brass with a half shaft, not aluminum, and no splines like many replacements seem to have. Some volume controls will also have an extra terminal, with a resistor connected to it, most Westinghouse sets from this era did, an incorrect replacement would not.
An incorrect audio output transformer can cause issues, but not intermittent ones, and they have no connection to the volume control pop. If the Philco transformer came from a set with a similar audio output tube then it should work fine, such as if the set had a #42 and the Westinghouse has a 6F6, if it came from a set with a #41 or a 6K6 then it will work but is a mismatch and the set will sound odd.
Regards
Arran