Thanks for getting back to me.
It’s very helpful to know which components are most likely to be causing the issue, because I don’t want to desolder any that I don’t have to and risk applying excess heat to them.
All of the capacitors are 15μF to match the originals. I just want to check – did you mean to say series capacitor C3? Because C2 appears to be in series with the filler rather than the tweeter.
I will check R6 after the capacitor, because no heat was applied to it in the soldering process so I think it is less likely to be the issue.