dholbach's test builds appear to have been without -proposed as they used libopenscenegraph99, which isn't multiarch (the libopenscenegraph100 in -proposed is), but I don't have any other theory for where the 19 comes from.
If it is multiarch-related, the fix would be to replace the libopenscenegraph[0-9]*:.*\s*install pattern with libopenscenegraph[0-9]*[:\s].*install
dholbach's test builds appear to have been without -proposed as they used libopenscenegra ph99, which isn't multiarch (the libopenscenegra ph100 in -proposed is), but I don't have any other theory for where the 19 comes from.
If it is multiarch-related, the fix would be to replace the libopenscenegra ph[0-9] *:.*\s* install pattern with libopenscenegra ph[0-9] *[:\s]. *install