Bullett M2 direct firmware download issue

I attempted to upgrade my Nanobridge M2's from 3.19.3.0 to 3.20.3.0 via selecting the latest firmware from the drop down on the admin page.  
However, I received an error:

Downloading firmware image...
Downloading
'http://downloads.arednmesh.org/firmware/ubnt/../aredn-3.20.3.0-ar71xx-ubnt_bull
et-m-sysupgrade.bin'
Connecting to 165.227.210.227:80
HTTP error 404
Firmware CANNOT be updated
firmware file is not valid
Failed to restart all services, please reboot this node.

Note the "..." in the url.  My choices in the dropdown were listed as:
aredn-3.18.3.0-ubnt_bullet-m-sysupgrade.bin
aredn-3.19.3.0-ubnt_bullet-m-sysupgrade.bin
../aredn-3.20.3.0-ar71xx-ubnt_bullet-m-sysupgrade.bin

I experimented with changing the download location on the advanced setting page from ​
http://downloads.arednmesh.org/firmware/ubnt
to
http://downloads.arednmesh.org/firmware/

I was then able to refresh the firmware dropdown and was presented with only one choice ​aredn-3.20.3.0-ar71xx-ubnt_bullet-m-sysupgrade.bin (no leading ../) which did work.  

Possibly of note, URL behind the link text in the error message contains an escaped carriage return character (if you use "copy link address" in chrome):
http://downloads.arednmesh.org/firmware/aredn-3.20.3.0-ar71xx-ubnt_bull%0Det-m-sysupgrade.bin

while the anchor text of the hyperlink in the error message wraps at the location of that character:
'http://downloads.arednmesh.org/firmware/ubnt/../aredn-3.20.3.0-ar71xx-ubnt_bull
et-m-sysupgrade.bin'

For comparison my HAP ac lite was able to direct download the latest firmware without issue.  It has the same download location (\ubnt) and had the leading ../ in the URL, but no problem.  Maybe a typo or stray character in somewhere?  

Edit: corrected dropdown options