I've noticed on my A7rII mounting lenses needs quite a bit more twisting torque than the A7II or A7r. Since Metabones adapters seem to be on the tight side I cautiously tried them on the A7rII. My later Mark IV (firmware user updateable) version will mount but it's very tight and doesn't rotate smoothly. An earlier adapter (no user update) can not be rotated to mount at all. It's a dead stop once you try to rotate it. So proceed with caution.