IIRC when Moodle 3.8 was released the DEV branch of AMOS was renamed to 3.8, but some time later instead of creating a new DEV branch the 3.8 branch has been renamed back to DEV and it seems like on that branch there are now both 3.8 and 3.9 strings mixed, or am I wrong?
Thank you Iñigo for spotting it, good catch!
The reason for this unexpected temporary glitch is that AMOS will be configured for the 3.9 development cycle only later today - that's the reason for the maintenance window starting at 17:00 UTC announced earlier. Everything should be as expected again tomorrow once the site is put back online.