Interesting that no error occurs when making a pause of 5 sec. I definitely will try that. When each sub is 300 sec that is not a great penalty. As for Version that works, I first detected the problem in Kstars 2.5.5. Jasem Mutlaq patched this version to make it work. I do not know what change he did, but I think all versions earlier than 2.5.5 is good. I have not found out how to specifically load an older version of gphoto2 and would love to see a procedure to do this.
Based on this tread i see the following Sony cameras: a6400, a7, a5000, a7s. Since I'm using the generic gphoto driver for my sony a5000 in stead of Sony DSLR i wonder if the problem is more widespread than Sony cameras?