An anti syphon is like a condom..its only 99% effective!
It will still draw liquid if the bottle is too full, or you fire the marker with the barrel pointing down with a partially full or more bottle.
Systems such as the Whispering Death expansion chamber, basicly trap liquid co2, while it boils off into gas (you can, or could get plexi glass clear ones so you could see this happening!) therefore preventing it from entering your marker.
If you do get liquid in your marker..it will a) Shoot hot ie: velocity will increase greatly. b) get covered in frost and c) possibly leak and or stop working all together.
If this happens, keep the marker horizontal or pointed upwards, and fire it off till little vapour is seen escaping from the barrel.
Or, let the marker sit until it has warmed up, and the seals have defrosted and become soft again.