It is a M96X TV BOX Android 7.1 S-905X Quad Core 2+8GB WiFi. I have this for about a year and never had any issue until now. I have not tried a fresh install (is there a way to preserve all your settings / addons?) I just dowloaded Paragons Linux File Systems for Windows and got access to the SD Cards-Update-Folder. Fortunatly I have a second one from wich I copied the System and Kernel.img so I could recover my device (now back on 8.95.7).
It sounds a little like the problems in this thread: Fail to boot with media_build (8.99.1). But I really don’t know what to make of it.