2015 Fox RC2 160/36 (650b) fork - negative air pressure problem
Thanks, moderators, for asking contributors to answer the actual question! So different from the millions of unmoderated, often tangential and perfunctory answers found on MTBR.

This problem occurs on both new and serviced forks. Fox's 40 mm downhill fork has pressure release micro-bleeders near the top of the legs, just below the dust wiper seals that get pushed in to activate. Since these are on both legs in the same location, and since sliding a zip tie past the wiper seals on both legs can usually release the pressure and return the stanchions to full extension, I find this statement, 


  air negative spring becoming over pressurized due to air migrating
  past the seal separating the positive/negative sides of the FLOAT
  assembly,


confusing, at best. And again, it's not just Fox Floats having this issue, Rock Shox users do, as well. I'm doubting there's an answer to how to prevent this, but hope in near future that Fox puts those micro-bleeders on the 36 if they can't engineer the problem away. 

Posts #104, 106 &amp; 108 on the link below has a contributor who shows how to modify your fork with your own micro-bleeders:

http://forums.mtbr.com/shocks-suspension/air-pike-lowers-psa-929695-3.html