After a quick google search i found this Kb article and I guess here’s the problem: Mapped network shares not visible in Macrium Reflect when UAC is enabled
Possible solutions are in the post (but I am not sure if they will work after you locked/unlocked your vault), and this can help as well: Cryptomator on Windows: Accessing your vault with admin priviliges
Of course a feedback of someone who is actually using Macrium together with Cryptomator would be very nice.