If it's doing it regularly, it may be an extractor problem.
Possible causes include, ammunition, magazine, spring,etc..
It means that the shell will eject on the left side not the right. Same way with rifles.
The gun does not always cycle. It also will not always eject the shell. These can both be potentially dangerous situations.
Shell-ejecting airsoft guns tend to eject their shells using a spring loaded system. once the bolt, or slide is drawn back after firing, the spring will force the spent shell out of the gun
Could be a multitude of things, from pits in the chamber to problems with the ejector mechanism. Have it checked by a gunsmith.
Gun shops, gun shows, want ad.
Many types. First, muzzle loaders do not use cartridge casings. Only autoloading firearms automatically eject a fired casing. Revolvers, and lever action, bolt action, and pump action firearms require a specific action by the shooter to eject a fired casing, as do single shot and double barreled shotguns.
The steel part on the top of the gun where the gun can eject the bullet/reload.
Your question is ambiguous, assuming by capsule you mean the shell casing then this is also not the case in every weapon. Shell casings are ejected when the weapon is fired if it is an automatic or semi-automatic weapon. Revolvers, for instance, do not eject the spent cartridges.
I had the same gun and same problem. I found out that because it is a older model that you have to use a little more force and speed when you eject the spent shell. It should work because i have the cheapest wal-mart shells you can get and mine works just fine.
A gun recoils when fired due to the need to eject the casing and to recycle the pent up gas