Hey I have a Trek Fuel 8! Great bike but I have to warn you, the Fox Rear shock I have completely sucks. I have had to rebuild it after every ride. Currently, my bike store is trying to get it fixed or replaced. The owners manual actually says you should rebuild it after every 8 hours of riding – that is ridiculous. I ride for 3 hours at a time and as I said, It gets "stuck down" (the travel is some how sucked out and the shock is worthless) after every ride I go on. Its a 5" travel shock so it should be able to handle southern CA moderate downhill and the like but it does not. The Trek is a tremendous bike with great geometry, it is sad the shock is so bad. I hope that helps… 😀
the shock on the bike is actually a really good shock, i think your having this problem because you are bottoming out to much, which means you have to much sag or you need a differant air sleeve, if you bottom the shock to much, it will cause the "stuck down" symptom you are having, the force from it bottoming out causes the air in the postive side to push past the seals into the negative side, which causes the piston to get sucked in a little from thier being a postive force on both sides of the piston.
also the recomended air sleeve seal service (and its only seal service, not a full rebuild) of 8hrs. isnt the reason your having "stuck down" issues, ive ran my Fox Float RP23 shock well past the 8hr. mark plenty of times without an issue, and i also dont think 8hrs for that service is ridiculous, if you look at some of the maintenance intervals for other shocks, youll see that 8hrs is some what the norm for rear shock maintenance