Sometimes it happens that when you build multiple times an image using wic and a partition which is not "/" or "/boot", you end up with duplicated entries in fstab.

Example wks:
include sdimage-bootpart.wks

part /recovery --size 500 --ondisk mmcblk0 --fstype=ext4 --label recovery --align 4


By building multiple times I (sometimes) got duplicated (or replicated n-times, depending on the number of builds):
/dev/mmcblk0p3  /recovery       ext4    defaults        0       0
/dev/mmcblk0p3  /recovery       ext4    defaults        0       0


I must admit I was tinkering with WIC variables and scripts (appending to WICVARS, playing with custom plugins), so it might be caused by some interrupted wic execution (WicError).