Sony 200-600mm focusing problem past 300mm

[Axutin]

Hey everyone, 

Ok so I have had this weird focus problem over year now, where Sony A9 with 200-600mm sometimes doesn't focus further than like 3-4meters away. Even if I try to manual focus the focus doesn't seem to move. So it feels like it has somehow shifted the focus range backwards closer than intended if that makes sense. So for example if I autofocus to tree 3 meters away and turn manual focus on, it shows that the tree 3 meters away is at infinity even though it obviously isn't.

Luckily this problem happens quite rarely, sometimes I can go month without seeing it, and it's usually fixed by removing the lens and putting it back on. Although sometimes I can see it multiple times a day. First I thought it might be just like some dust or dirt on connections but after dealing with it for over year now I'm 90% sure it's not that. Sometimes removing the lens and turning camera back on doesn't help either.

Also I tested my 200-600mm on my dad's Sony A7RIII and could replicate the issue, so the problem seems to be on the objective, not on the A9. 
Also noticed that when that problem occurs the autofocus works normal up to 300mm, and after 300mm the focus breaks and only focuses on subjects close to camera like 2.4-5meters away. So it seems like 300-600mm range is the problem here, but no idea what causes it.

This focus problem has been present with both firmwares, so the newest update didn't fix it. This might be hardware related problem.
Also when this problem occurs the camera body still recognizes the lens, so it's not like it loses connection.

I searched all the forums and couldn't find anyone with problem like this.  

 

Videos of the problem. Part 2 shows the manual focus and camera thinks its focused at infinity when focus is on a tree like 3 meters away.

 

 

[Axutin]

Anyone know what could cause this? Weird thing is that sometimes it even happens when camera is turned on, so focus works perfectly for example 5 minutes, and then suddenly it just stops focusing beyond like 5 meters and even with manual focus you can't focus beyond that 5 meter.

[grsnovi]

Is it possible that you have the limit set wrong or that you are somehow hitting the switch (or the user-configured button on the lens)?

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[Axutin]

2 minutes ago, grsnovi said:

Is it possible that you have the limit set wrong or that you are somehow hitting the switch (or the user-configured button on the lens)?

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Hey,

You can see in the video the Focus limiter is set to full. 

I sent it to repair and they said it's faulty zoom position potentiometer. 

[grsnovi]

37 minutes ago, Axutin said:

they said it's faulty zoom position potentiometer.

Are they going to fix it under warranty? Or have you had it too long?

[Lez325]

On 3/22/2023 at 12:21 AM, Axutin said:

Hey,

You can see in the video the Focus limiter is set to full. 

I sent it to repair and they said it's faulty zoom position potentiometer. 

I was about to suggest that being the issue- It sounds like an expensive fix , Hope you get this sorted these are very capable lenses

 

Les