Muse solo Strings make glissandi almost on every note. Bug?

I´m working on several pieces for solo string instruments. What I´ve noticed is that the solo strings (Muse Strings) perform a glissando almost on every note. But I´ve seen
many score videos where this is not the case, so probably I´m doing something wrong? Do I have to make any specific setting in order to avoid that glissandi? It is nowhere indicated in the score, so I have no idea why this happens.
This is not the case with string orchestra sounds, but only with solo. Do you have any suggestions what I can do about that?