[toni-a]

My 28f2.8 is acting just like if there was an extension tube, its optical performance is unchanged, it focuses now very close with loss of infinity focus.
Anyone knows what's the problem with it?
Repairs in Qatar are practically non existing except for new expensive lenses besides i doubt they could have spare parts for it

[Klaus]

Even at room temperature?

[toni-a]

At all temperatures yes, I am fearing a displaced element as the lens seems perfect when handling, aside shifted focus range

[Brightcolours]

So when you put the lens in manual focus, it does go from stop (closed focus) to infinity without issue (i don't mean if it focusses at infinity, but if the mechanism travels all the way to infinity)?

[toni-a]

So when you put the lens in manual focus, it does go from stop (closed focus) to infinity without issue (i don't mean if it focusses at infinity, but if the mechanism travels all the way to infinity)?

yes in manual focus it goes all the way to infinity but the lens is focusing at 1.5 meters, when at minimum focusing distance its at around 15-20cm from subject

[Brightcolours]

And I guess it does this on all cameras. Beats me, can't find if the lens has floating elements or not.

[Klaus]

The 28mm f/2.8 uses a linear extension mechanism I think - with infinity being available at a fully retracted state.
If it does retract as normal, there's something wrong with the optics - which is, however, odd. This is one of the most simple lenses out there.

[Rover]

Sounds like stuck focus. My Tamron 45/1.8 had an outwardly similar issue, but after a time it locked itself on MFD and wouldn't focus manually or automatically. Admittedly that's a very different lens.

[photonius]

So when you put the lens in manual focus, it does go from stop (closed focus) to infinity without issue (i don't mean if it focusses at infinity, but if the mechanism travels all the way to infinity)?

yes in manual focus it goes all the way to infinity but the lens is focusing at 1.5 meters, when at minimum focusing distance its at  around 15-20cm from subject

Is the image at 1.5m in good normal quality?  Is the minimal focus distance of 15-20cm less than what it normally should be for this lens? That might indicate that the whole group of lens elements (given it's a simple extending design) is ok. Then perhaps the whole lens unit shifted in relation to the focusing ring. 
I have a Samyang 8mm fish-eye. Those were notoriously poorly calibrated. Mine was - when set to infinity, focusing at 3meters, infinity was not in focus.   To fix this, one had to remove the rubber focus ring, loosen a screw, turn the focus ring further (to the right position so that infinity was now really infinity), tighten the screw again, done. Basically with this one screw you calibrate the focus ring with distance scale to the lens group.  I am wondering if your lens has a similar simple adjustment method, and maybe something got a bit loose with one (or two?) screw that fixes the relative position of the two units (the focusing barrel and the lens group). Maybe the focusing barrel was turned too strongly?   Could one fix it by turning the focusing barrel strongly in the opposite direction?     - Of course, I would not recommend doing the latter, unless I was really sure how the lens mechanics work.   
Here are also some other instructions for other lenses how to calibrate to infinity focus.
https://richardhaw.com/2017/10/21/repair...ration-12/.