One 5400ZL 14.47 doesn't update ROM to 12.20

[Mike T.]

I have one 5412ZL that when updated to 14.47 (Following the correct upgrade path to get to this level per 14.47 instructions) the ROM stayed at 12.17. None of the other 5400's have experienced the problem so far and I have 60+ 3500YL's that did not have any problem. Some were done by hand, some with PCM+ (locking PCM+ at 13.71 before upgrading to 14.47). I have heard others in this forum booting to the secondary once and then back to the primary when this happens. I was wondering if this was a plausible fix for this issue?