Can't recall as I haven't used it in a while, but I assume Paragon is allocating letters according to the partition table position.
That may be different from the lettering inside the o/s registry.
Try the Paragon boot corrector - select "correct drive letters in system registry".
I assume your o/s originally declared themselves as C when you booted into them ?
Boot corrector will load the o/s registry and show you how the mounted devices are listed there. It allows you to change the o/s drive letter back to C ( or whatever letter the o/s used to declare itself as. )