Hi Mike-
First- I have tried every combination to get it to happen with a pattern and the only thing I notice is that is happens more on editing saved listings than on new ones- but I have seen it happen on new listings as well. Also, when I have noticed the option missing I tried doing to fixed price and then to auction and back to fixed price but it didn't change it.
Secondly, I did put in a request and the guy who returned and answer educated me on how Best Offer works rather than IF it works. So-I am glad to see that there are others showing this problem.
Thanks for your attention to this matter.
Annette