Portamento when using solo string instruments for a string quartet is too much and unnatural

I am writing a string quartet. I am using MuseSounds for the instruments. In certain passages an unecessary portamento is added to the playback. It would be nice to have the option but it is automatically added and adds an uncharacteristic but very noticeable articulation. I followed a previous recommendation avoid the excessive portamento in the first violin by choosing to have the "Violin 2" sound used for both violins. This happens in the viola and cello as well however. Any help?