Before I answer the question, with the ejection at 3- 3:30, was this with the spent cases off the defector and being deflected semi forward?
With the orange spring, is the cases now missing the defector on the way back instead.

Bluntly, the spent case should be rolling off the face of the bolt as the rear dead blow effect of the buffer take place, which causes the rearward ejection path of the spent case initially out of the port window.  As for once it out the window, then it's a matter of if it tagging the defector or not.

If the stroke is not controlled correctly (too fast on the way back), then as the buffer comes back and tags the back of the tube too hard, instead of a dead blow effect at the back of stroke, the buffer just sling shots off the back of the tube instead, and this cause the forward ejection path out of the port.  If the stoke is too slow on the way back for no real buffer impact to shift the buffer weights back hard to cause the dead blow effect, then same thing and not enough rear stall time for a clean pivot off the bolt face before the bolt starts moving back forward.

As for myself, if the heavy buffer and extra tension spring is not causing a semi short stroke effect/problems with any of the ammo you are running cycling correctly, has not increased the felt recoil of the rifle, and has the brass being ejected out the back and not into the guy to the right of you at the range, is does scream 'Winning Combo".  Here, it does sound like the cases are still being ejected rearward, but the stall is just a touch shorter, and the case  are being pathed out just enough to miss the deflector instead.

ON the T56, smoke the hell out of bullet itself with a sharpie marker, and also the neck of the case as well.

Drop the round into the chamber by hand, walk the charging handle down, then use the FA to lock the bolt home.

Now remove the round, trying to prevent the tip of the bullet from getting scratch up by the barrel extension lugs on the way out, and see if the bullet is embedding into the rifling at loading, or if the last of the chamber reaming it too short for the ammo's case lengths (scrap marks in the sharpie smoking that you did the bullet before hand).


If the old surplus  ammo is all tarnished up, them throw the live ammo into a media tumbler to polish the ammo/cases.
Hence the problem could be that the tarnish on the case is preventing a clean release of the spent cases from the chamber at unlock.

Note, I can't  even begin to count the amount of Chilean 308 surplus ammo crates that I had to throw in a tumble to clean that crap up decades back, to just begin to check them for any cases that had corroded to the point that pitting on them was too deep, that you dare not firing some of them to begin with.
Hence, it came in a huge wooden crate that itself was on it last legs, that had paper boxes in the crate with no plastics seal'g of any kind, and pretty sure that when the stuff was boated into the states, instead of it being in the cargo hold, the just drug is in the water behind the ships instead (bad storage, and why it was suplused off and sold so cheap to begin with..
So the rounds on the bottom of the crate looked something like this,



Also, may be too much buffer mass for the ammo, and may need a lighter buffer instead for the surplus ammo.


To add, when buying surplus ammo, try to figure out what the country is surplussing it to begin with.  In the case off say Port and such, it was because the country was moving ways from the 7.62 round, and selling off the extra surplus of ammo that had instead. With the Chilean ammo, that country had not yet moved into the 5.56 heavy yet at the time, and that 308 ammo was being surplussed off due to it being storage badly instead.

Still seeing a lot of tarnish on the cases from the Acid in the box cardboard leaching onto the brass in the above photo from the decades of storage, and giving that ammo a tumbling will remove the light layer of brass tarnish to polish the brass back out to fresh factory produced smooth conditions (read polished brass ammo will extract a lot cleaner out of the chamber when the cases are polished smooth again).

Not sure what size tumbler you have, but if only a smaller one, then tumble a few boxes of ammo and see just how much of a difference it does make with your rifle.
Hence leave the ammo that is sealed in the plastic wraps alone for further long term storage until you are going to use it, and as you cut open a plastic wrapped pack to start using that ammo, then just media tumble that ammo  only.  The acid tarnishing is a lot slower than say humidity tarnishing, so just tumbling the ammo in the packs as you plan to use it works just fine.  As for the cardboard boxes that the ammo come in, just reuse them again after the you pull the ammo back out of the tumbler.  The case will  have media tumbler polish on them, so that will work fine to keep the acid from leaching back on case to start tarnishing them again short term instead.

And yes, even say Port and SA ammo that is in plastic sealed bundles will run into the same problems, since the  thin cardboard boxes that the ammo packaged in inside the sealed plastic packs, is not acid free on some of the older surplus.

Hell, when I am reloading jacket/plated bullet ammo through a progressive press by the thousands each session, even since I just store the lots in ammo cans with a hand full of Desiccant thrown in, after the ammo is reloaded through the press, I will throw it in a tumbler to re-polish and get any case lube/finger oils off the case before putting it in the ammo cans for storage until I go to short it.
Note, do not throw casted lead bullet ammo in a tumbler.  The media will just embed into the raw lead of the exsposed bullet surfaces and will end with huge mess instead.