Nickie Fønshauge found a bug in Kontakt: for scripts loaded in the first script slot the code which handles note release is not always run. For scripts such as SIPS which in some situations depend on delaying the release of a note this can cause problems. This manifested itself with frequent stuck notes when the SIPS Legato Script V110 was loaded in the first script slot on instruments with looped samples. On instruments without looped samples the effects are not as clear but I believe the voice count can be higher than normal and it's not certain whether the transition sound is affected.
Please only load the SIPS scripts in script slot 2-5 not to be affected by this Kontakt bug.
Btw. If you happen to think that this Kontakt 2 bug is serious enough to warrant a fix, why not speak up in this thread on the NI Forum.