I was never given a satisfactory answer last time I posted about this issue... While I understand it is related to syncing I do believe it is still a vectric bug which needs to be solved. All the other files I have on my computer are also syncing and I don't regularly get locked out of any other program files.
This particular file is 37mb.
In the meantime I will simply disable syncing while I am working on projects and then try to remember to re-enable syncing before I leave the office for the day. (Not a good solution as I'll forget 90% of the time.).