When I attempt to save a title to one of my lists, I frequently see extra titles I didn't select under Add items to a list. If I try again after refreshing the page and clicking Save to your lists I'll see even more unwanted titles. These extra titles appear to be originating from other Koha users. It's like Koha is assigning a timestamp of some kind and expecting it to be unique, without checking if the selected titles are coming in from different users/IPs.
Which version of Koha are you using? Are there steps this can be reprocuded easily?
There have been no other reports of this and I can't reproduce the issue. Marking WORKSFORME. Please reopen with more information if this is still an issue.