Fringer adapter: Nikon lenses on X-T3

[JimB]

I have an X-T3 that I use for concert photography and also for bird photography. For concerts I use a Nikon 70-200 f2.8 GII. For birds I use a Sigma 150-600, Nikon mount. To adapt the lenses to the X-T3 I have a Fringer FR-FTX1. It works flawlessly with the 70-200, and initially it also worked flawlessly with the 150-600. However, recently the 150-600 has been having trouble acquiring focus. Sometimes it will lock right onto the subject, but more frequently it hunts and then quits with the subject completely out of focus. I can use manual override to re-acquire the subject, but even that's not a sure thing. As I said, this problem is somewhat recent and is perhaps progressive. The lens is fine; I've been using it on my Nikon D7100 with no issues.

I emailed Fringer and got this reply: "In that case it indicates a power supply issue which is not rare when using a small battery to power a big lens. But since the most power consuming moment is when lens IS is just started, keep IS in continuous mode sometimes may fix the issue." I should note that I have the battery grip, so in fact I'm using three batteries.

Does this sound familiar to anyone? Any suggestions?

Edited April 1, 2023 by JimB
typo