I hooked up my 150-600 C to the dock last night to make a few adjustments and noticed that there was a new firmware version available (Ver. 1.01) It's supposed to improve AF when using the TC-1401 TC and I thought it said (improve other issues) or something to that effect. So I went ahead and ran it even though I don't have a 1401 I figured it couldn't hurt....Wrong. I used the camera and lens this morning without issues. Just a little awhile ago I thought I would try it with my Kenko Pro 300 1.4X to see if there was any improvement there. Well when I turned the camera (7DII) on I got an error message "Firmware Update Failed" ?? tried another Formatted card and the same thing. Took the TC off and camera works fine. So then I tried my Canon 1.4X III......got a "communication error" message and the AV read 00 so that's a no go as well. I would suggest that if you use this lens with a TC other than the TC 1401 that you wait to update the firmware until it's understood what's going on here. I will call Sigma one day this week.

