Just downloaded 4.6 and checked for firmware and it's saying the EXT0CB6Q is the latest. Looks like the pulled the D update?
I don't know about you, or why you didn't get "D."
I was initially mystified that my version 4.5 didn't just update itself to 4.6.
So I went to the Samsung site, found the 4.6 upgrade and did some reasonably careful reading.
Finally, I unzipped the file and installed 4.6. It then showed that the new firmware version " . . . D . . . " was available, so I went through that hoop, also.
Everything seems to be just happity-joy and wonderful.
The 4.6 version is apparently good for the 840 Pro as well. I've therefore got two more machines to putz around with and get this behind me.
AFTERTHOUGHT: Maybe you spoke too soon. The installation process meant at least two reboots, and the firmware update required a third. Re-enabling RAPID needed a fourth restart.
Also, I don't think it will update the firmware with RAPID enabled. Like I said -- I DID do some reasonably careful reading before jumping into this.