A few weeks ago the Z6/Z7 v.3.11 firmware update was published.
No need to apply it if you don't have the MB-N10 grip (fixed incorrect switching between battery A and Battery B in the grip when one got exhausted)
A caveat was issued (in the instructions) on a bug regarding "fine-tuning values selected for AF fine-tune > Saved value were not correctly applied when pictures were taken". Bug was already present in firmware v.3.10, and was still uncorrected in v.3.11.
four days ago the bug was fixed, and release 3.12 of the firmware was published. With this bug fixed, update v.3.12 becomes a MUST!
Same bug on the Z50, which was corrected with release 2.02.
Ciao from Massimo
