Welcome to the super confused club.
I don't recall where I got it, but my Obi 1062 is currently running 5.1.11 (Build: 4858EX.1311).
The firmware file itself is labeled: OBiPhone-5-1-11-4858EX-198839.fw
It's the highest number for the OBiPhone 10xx series that I've seen, and as I mentioned, I have no idea where I got it, but it appears I downloaded it on July 12th of last year...
EDIT: Now I know where I got the new firmware. It was from another thread here (just a few messages below this one). Here's the link to download the firmware:
Quote from: Dan-Voip on July 06, 2018, 08:39:03 AM
Version 5.1.11 (Build: 4858EX.1311) is available at http://fw.obihai.com/OBiPhone-5-1-11-4858EX-198839.fw