OK, here is an update on the situation. While I could not create a backtrace, I observed that the crashing always occurred at the end of the transfer, after all books had already been copied and this job is finished.
I think next is the phase, where the metadata are written to .metadata.calibre In all cases I observed, this file had a length of zero bytes. When I batched the transfer in smaller portions, I could see this file grow to more than 200MB, but this is still with about 5000 books. So the file will grow much larger as more books are added. So my hunch was that somehow this file was growing unexpectedly big and caused the routine writing it to crash the whole program.
I then went to investigate the file and discovered a whole lot of columns that I did not use. They had been created by the plugin ZMI (Zotero Metadata Importer) when I tried to import some metadata that I am maintaining in Zotero. In the end, this did not work and so these columns are not necessary. I removed them from the Library database and tried the whole export once again. This time it worked! I could export all the books to the device and can see them there and also in Calibre!
I am not sure if this observation is correct, but at least it solved the problem for me.
https://mobileread.cdn.speedyrails.n...t/thankyou.gif
Thanks for all your suggestions,
Ctop