my top won't go all the way down. What can I do?

take a shopvac with the small tip and suck up any spiders, leaves, dendrites....dirt, sand spores anything that would stop full motion~ lubricate the joints with tri-flo....just a few drops, that stuff goes everywhere~

Agreed. Foreign objects in mechanism or stow compartment maybe

as far as I know these systems are "hermetically sealed" and should not loose any fluid~

Is this a common problem for Audi's?

Hello , Audi top stuck , try this with the ignition on cycle manually the entire system , but in the process look at the right rear section where the top will tuck in , look carefully you will see 3 sensors check them make sure they move freely and not stuck , then most mportant check rear seat belt make sure they are fully retracted and the red securment button is not stuck in other words make sure all rear seat belts are in correct position , then put in back to normal position , turn off switch , also make sure your two fuses are good , then lock the system manually , then once again cycle the system entirely all the way do not move any sensors or you will fool the computer , cycle the top all the way turn off your ignition and try it , if still does not work then recheck the side sensors , they are not too difficult , good luck