Hi Andi,
I made a video capture from opening Vienna Ensemble Pro 7 and Sibelius to setting up the Violin 1 and playing it with techniques, while switching over to view the VE while playing. You cannot hear the audio playback in the video (something to do with my audio system and my video capture software), but you see the patch changes in VE as it's playing in Sibelius.
Notice that the Tremolo patch is working, but not switching to Arco. At the very last play example it goes to Pizz., and the next bar technique is set to Arco, but it goes right back to Tremolo instead of Arco.
I'm pretty sure I have everything in the Sibelius setup and VE assigned properly. I also verified my Vienna Ensemble Pro .dlls are in both my vst64 and vst32 folders (otherwise they wouldn't show up in the Devices window).
Here's the link for an .mp4 at DropBox: https://www.dropbox.com/scl/fi/1r2co743cu3u5klw9jy4k/Violin-1-and-Sibelius-Test.mp4?rlkey=xtlfa89hoj7sz5wg7de8wmqu7&dl=0