Garage door lock barrel problem

[Spade]

Hi all.
One of the lock barrels on my garage door will come out with the key when I turn it to the locked position.
I am worried that it will come out when I'm traveling.
Anyone know how they are kept in place please.
Photo of one below

 

[SandraL]

In your picture the last brass coloured tab should hold the barrel in.
A special long key can be used to remove barrel when in the unlocked position.

 

[Two on Tour]

Sounds like all the tumblers are jammed.
If you you take the barrel out and remove the key, do all the tumblers stay in flush with the barrel body or do they protrude out from the barrel body ?

 

[Spade]

At work,but I'll take it out tonight and have a look.
Thanks

 

[Spade]

The tumblers seem to be working fine and the brass tab is out so i am assuming that the innards of the plastic handle are damaged so the barrel won't stay in place.
I will source a new part
Thanks for the help