So here is where I need some education, not being that familiar with what sophia2 provides to a PAL system.
This is what I've gathered: You have two NTSC 600XL boards you converted to PAL. You know PAL 600XL composite output (on PAL manufactured boards) is great. You even have a dead PAL 600XL you can use as a reference. You did not install the passive components needed for PAL video because sophia2 provides these? That's where I'm confused.
According to the official, and probably not correct schematics, PAL boards should not have W2 and R140. W2 being removed feeds into U24 and also needs a R120 pullup. W2 is what ties the GTIA OSC line through the crystal Y1 and then feeds into GTIA PAL line.