Depending on character models present in your studio, frames may drop even with decent VR Ready PC due to a large number of polygons.
Please change the model to ones with fewer polygon counts, reduce the number of people in the studio or use a PC with higher spec.
Items that always display a video preview are heavy processing, so delete them when they are no longer needed.
Because the physics operation is performed for each sub item,
too much may cause the processing to become slow.