I had a similar issue but caused by a different reason. The relevant thread is below, ignore the image disk references in my posts.
https://www.mobileread.com/forums/sh...d.php?t=316534
I fixed my wifi issue by manually installing a firmware, perhaps this might work for you. My last post #13 is the summary of what I did, (ignore the disk image reference).
Edit: Interestingly, I was using the same firmware version as you prior to my issues.