Make sure you install the black magic decklink software after media composer, it wont install the plugin for Avid if its not installed, and make sure you run Avid as an administrator on first run. Also check the MAC’s security tab in settings to allow the driver to run.
What editing software do you want to use? At that number of users at 4K you will need to go to either Avid Nexis, EditShare or Facilis Technology. Switching will be an important part of it. You should engage a system integrator as this sounds like quite a large project. HTH
You will need to NEST the V2 layer and apply the fade to white in the nested track and re-apply the pic in pic on the V2 track above the nest. Look up Nesting tracks in the help.
Have you tried cleaning out all of the MCState files also you SHOULD NOT use settings from an older version as this will cause issues. Clear MCStates and use a new user.
I would not wait until the day of the shoot as you might get a thunderbolt RAID and not have the right connections. Also exFat is crap on spinning disks as it was produced for Flash drives etc. Double check with the editor directly what their requirements are and don’t assume anything. If you are doing the main copy on windows NTFS will be much better. Macs can read NTFS. There are utilities for very little money that can R/W to NTFS on MacOS.
Sounds like good old Betacam dropouts, not much you can do as the tape has been damaged at that point, make sure the VTR and Computer have reference going to them so they will lock to each other can sometimes make the dropouts appear less gruesome.