Philip. 2B or not 2B. In this case, I'm referring to the stability improvements (and others) at 3i. USAF is declaring IOC for their fleet with 3i as a baseline.
Lt Gen 'Dog' Davis has already alluded to the 2B fusion issues and workarounds from 2015 but the jets are now operating 3i which is better all round and doesn't exhibit the instabilities reported in 2B.
If the USAF are declaring IOC this week (likely, but not guaranteed) then I trust their due diligence in testing every aspect of the operational benchmark they set themselves.
Worth bearing in mind that most of these major 'deficiencies' are software based and that there is more than one drop of 3i software.