JabRef firefox extension: download linked online files error

JabRef version

5.9 (latest release)

Operating system

Windows

Details on version and operating system

Windows 10 22H2

Checked with the latest development build

• I made a backup of my libraries before testing the latest development version.
• I have tested the latest development version and the problem persists

Steps to reproduce the behaviour

The JabRef firefox extension successfully downloads linked online files but I found a case where I got an error

1. Go to https://royalsocietypublishing.org/doi/10.1098/rsos.220519 using firefox
2. Open a JabRef database
3. Click the button 'import references into JabRef" in the firefox URL bar
4. Enable "download linked online files"
5. Click the import button and see the error appearing

The weird thing is that the "Open File" link in JabRef is perfectly working (it is pointing to the online PDF link).

Version of Firefox extension:

Appendix

...

Log File

Paste an excerpt of your log file here

[Siedlerchr]

403 as status code means forbidden, this means JabRef cannot download the file as the server denies access.

That's not true (as far as I can see) because of following reasons:

https://royalsocietypublishing.org/doi/10.1098/rsos.220519

1. if you click the "view PDF" button manually in your browser, you can download the PDF

OR

2. if you click the open file icon in front of the imported entry in the JabRef database, you are redirected to the same PDF as in 1.

So both a webbrowser or JabRef itself (!) can access the PDF. So I don't know why 403 is received then...

It seems to occur with all papers from The Royal Society,
Here is another example that gives the same error:

https://royalsocietypublishing.org/doi/10.1098/rsos.160342

I just found this error is not only there for The Royal Society papers, but also for ResearchGate papers.

Here is a paper that gives the exact same error, but clicking the button "Download full-text PDF" gives access to the PDF.

https://www.researchgate.net/publication/223359175_Taphonomy_of_insects_in_carbonates_and_amber

The strange thing is that JabRef has saved the link to the PDF which works perfectly (it is pointing to the online PDF link).