how to tell diff between pin lock and ball lock

I am having difficulty with a keg... not pouring correctly. I can see there is air intrusion into the draft line.
I have changed all o-rings and seals, connectors, everything... even swapped draft lines to make sure... it is coming from the keg/disconnect somewhere.
I have ensured that the connections are all tight... it is really pissing me off!
The keg itself is a bit shorter than the other kegs I have and am wondering if there is something else (type of keg) that I may be overlooking.

Any additional thoughts/ideas are MOST welcome.
Thanks!

Sounds like the beer out (liquid) dip tube o-ring may be compromised. Have you removed the post and dip tube to check it out?

I did verify the seal on the dip tube and all connections and cleaned everything that I could tear apart and inspect.
I am still at a loss.

I have ordered all new piece/parts in hopes that I have missed something, but so far... no luck