I have the a very similar problem. But it is not important wich module want to take the picture - even frame and focus "take one" puts this error:
[DEBUG] [Camera Thread] Canon: Error in EdsSetPropertyData (PropID_Tv 0x0C) Error: EDS_ERR_DEVICE_BUSY
I use a Canon EOS 70Da for this. This problem does not occur with my EOS 500Da.
In some other threads i read someting about mirror lock. I tried every combination (mirror lock in SGPro above zero and mirror lock enabled or disabled and the same with SGPro mirror lock 0) but the problem always exists.
The solution metioned by Marcin (Switch B) does not make any difference.
It is okay in normal sequence but it fails the plate solving, wich is kind of not so good...
Are there any updates about this? Any workarounds?
Thank you very much!