Accumulator pistons are supposed to be a snug fit, especially if you can't pull the piston straight out without the rocking side-to-side. That's fine. Worry if the pistons fall out rather easily.
I believe I have a spare VB
of each style, but I'd forst check if Sonnax makes a repair sleeve kit, or a reamer and larger valve.
The stuck valve could explain the late shifting, but I can't see how it could block second.