I have been running Time Machine on shares for 2 Macs in my house without incident. I added a new macbook (and 3rd share) to my Drobo 5N about 6 weeks ago. Every 1-2 weeks I get the error:
Time Machine completed a verification of your backups on “Drobo5N”. To improve reliability, Time Machine must create a new backup for you.
Can anyone suggest why I may be encountering this issue? FWIW, the macbook, drobo, and WiFi router are all in my home office. I have no reports of networking issues on any of the Macs or smartphones.
Drobo Dashboard: 2.7.0 
Drobo 5N Firmware: 3.3.0 [8.75.76511]
SSD on macbook is 256 GB, share is 512 GB