Import stuck at 0% (but creates the first item correctly)

EDIT OOH - so I just figured out that the import only gets stuck for items that once existed but that have been deleted (not only trashed!). If I just import unused IDs, it works fine. Any idea what I could do to fix that? There are no "trashed" items visible in the flexicontent backend. (I do have access to the SQL database itself, tho, and I'm not afraid to use it - if I know knew where exactly.)

Hello, I was hoping someone could help me with a curious problem: 
The import seems to be working fine up to the point where I should "continue import task", previewing the content from the CSV file correctly

But when I click, it gets stuck at 0%:

Even more curiously, the first item is imported correctly.
The only log I knew how to find () just says "2018-06-18T12:48:32+00:00 INFO Imported item no: 4. titled as: 'abaxial'" for the first correctly created item.
Can you help me find out what's going wrong? (and possibly fix it)
Thanks!
Peter

Hello

At Joomla 's Global configuration set "error reporting" to "Maximum" and retry to import
and see if we get some more information out of this