JabRef 5.0-dev--snapshot--2019-04-03--master--a273eb1fa
Windows 7 6.1 amd64
Java 1.8.0_201

• [+] I have tested the latest development version from http://builds.jabref.org/master/ and the problem persists

When importing from Medline, there is the import and one canceled import. Already in version from 2019-03-30. It does not put a strain on the actual import.
Steps to reproduce the behavior:

1. use the Pmid of a medline entry e.g. 30137510 to search medline
2. import the article
3. you will notice the importing, but also a message "import canceled"

Paste an excerpt of your log file here