When reopening JabRef, the field "Readstatus" is empty for almost all entries.

I've just installed the following version of JabRef on my Windows machine:
JabRef 5.0--2020-03-06--2e6f433
Windows 10 10.0 amd64
Java 13.0.2

Steps to reproduce the behaviour:

1. create an entry of whatever type (e.g. article)
2. set the "read status" by

• either right-clicking on the entry > Read status > read (or skimmed respectively)
• or typing it into the field "Readstatus"

3. save the project
4. close JabRef
5. reopen JabRef
   → read status is lost

The error log is empty.