never stop rendering

[hiroki_okamoto]

When rendering , close v-ray buffer window , after that
I could not reopen rendering window.
Is is bug?

[nikoleta.garkova]

Closing and re-opening (or minimizing and returning it) the VFB should be possible while rendering. Can you post a recording so I can see what exactly is happening?

Moreover, have you tried bringing back the VFB from the Asset Editor's button, see screenshot. Alternatively, you can try from the V-Ray tab > Frame Buffer;
Additional details about your setup would be greatly appreciated (as requested in your other posts, and do share if you are using a multiple-monitor setup).