text around cylinder surface

[micheus]

@micheus: that ring is made like seen in #9 - hard edges everywhere, I used smoothing in Kerkythea later (Loop Division or something like that)

That's would be the problem. The subdivision tool in Kkt doesn't works well.
Tip: if your object is not smooth enough to just apply Smooth in Kkt, then is good idea you subdivid it before export or during it (there is a option in the exporter).