ID 228447 - STMap produces soft transition artefacts using all filters except Impulse

Problem summary
STMap produces soft transition artefacts using all filters except Impulse

Customer reported version
nuke.10.0v1

Customer reported platform
windows7

Steps to reproduce

Load attached STMap.nk

1) Open STMap.nk

2) View STMap node , see soft artefacts at edges from Roto node if set to any filter except Impulse

3) View STMap if set to Impulse, no artefacts

Reproduced by support
MacOS 10.10.2
7.0v1-10.0v3

Expected behaviour
No soft artefacts with filter settings (other than Impulse)

Actual behaviour
Soft artefacts created by STMap from edge of Roto shape

with all filter settings except Impulse