[Arran]

First I would double check your work, as a bulk recap, rewire, and re-resistor job is fraught with possibility for anything from something being wired to the wrong terminal, to a wire left off, to a missed solder joint. This is why I encourage people to perform a test power up if possible, to establish a base line. After that it's best practice to start from one end of a set, and work your way to the next, whilst recapping, rewiring, etc, and if possible to test the set in-between moving on to the next step, to see if there is an improvement, or if it still works.
When you mention "updating" the tubes, do you mean that you replaced them all? I have found that it is very rare for every tube in a set to need replacement, aside from a battery set. Even in the case of an individual tube unless it's shorted, gassy, or burned out, the radio will still work unless it has very weak emission. With the replacement tubes have they been tested? Do you know that they are all good?
Have you checked the coils? Is there continuity across the primary of the antenna coil? Have the grid cap leads been replaced? How are the solder joints on the clip, and the other end? That is a weak point on double ended tubes and can cause a lot of headaches, like volume drops, etc.
With regard to the volume pot, is it a replacement? Is it a linear or a log pot? What resistance is it? If it's giving trouble I would examine the solder joints on the terminals, and also make sure it's wired the right way around. I would also give it a cleaning with some alcohol spray.
Regards
Arran