Yea I don't think they are considered "serviceable" that being said what likely happen was when you tried to remove the truss nut it felt like a dual-action when the nut reached the underside of the walnut plug and stopped, so without scoring the poly and softening the plugs glue it will indeed crush the plug, crack the poly and probably would've cracked the fretboard if you used too much force before realizing that this was the issue.
Here's a pic after the walnut plug was removed with the truss nut removed.
View attachment 5414765
I drilled through the old nut and cut a spacer from it to use instead of washers.
View attachment 5414766
Alternatively you can use a long bit
to cleanly remove the plug instead of using the heat softening glue method.
StewMac also sells a truss rescue tool.
This HERE is NOT A Crafted In China Classic Vibe, it's a Crafted in Indonesia one with a 4mm nut / single action trussrod.. You CANNOT REMOVE THE NUT on a CIC CV. Can you please acknowledge what people tell you and stop insisting on telling me to do something that is NOT POSSIBLE? The nut doesn't go OUT on a DUAL ACTION TRUSSROD... I'm getting annoyed.
" All I can advise is to enjoy the hell out of the instruments you already have that make you feel good or better.