Alacant, did you ever get to the bottom of this and solve it? I'm having exactly the same issue, with the same camera.

Constant errors of "[ERROR] Exposure failed to save image... Unspecified error" and having to make a second attempt. It does sometimes work (about 50% of the time).

I found this in github for a Sony camera:

github.com/indilib/indi/issues/251

So will try turning LENR off tonight. Also, I see there is a delay option to put between taking frames so I may see if that has any benefit.

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