The fix for the not enough space issue on the EX2 Ultra is simple.
1) Navigate to Settings>Advanced>Open Power User Preferences in the Resilio Sync Web UI.
2) Change disk_min_free_space value from the default (0.0) to 0
3) Click the "Close" button after editing the above value to 0 (zero). Close the window by clicking the X.
3) Reboot the NAS.