i used simple placer and follow too.
blackmagic ultrastudio 3G + last desktop video setup 12 + sony 6400
bigsur + MLb5.10b2 + M1macmini 16Gbram
I notice a slowing down of the video signal, although in the rendering performance monitor and source performance monitor and activity monitoring NO any red lines or troubles
example
ps also mini bug with ultrastudio 3g
pps crash reports