The Poser primitives are built with split edges, so that their corners will be sharp in Poser renders.  This means that the end caps of the cylinder are treated as completely separate objects, so Poser doesn't even try to keep the edges together.

Here's an alternate cylinder object.  I've attached it as a TXT but it's
really an OBJ ... save it as CYL.OBJ then import it to Poser and resave
as a PP2.   Its edges are joined and slightly beveled, so it should behave
better with displacement than the native cyl, but it won't look 'sharp'.

And yes, you can redistribute and sell things made with freeware
modelers!

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