Thank you for all your responses!
Indeed I did raise the question with Kindle customer service, but as so often, when something is not solvable by protocol, they weren’t very helpful. They took my question/complaint as a suggestion and „forwarded it to the development team“ where I am pretty sure nobody really cares or cared(since that was some time ago)...
So it is possible that my Mac is causing this, but in all seriousness, I wouldn’t know where to look (and CS wouldn’t tell me
)...
So, stuck again...