Keep in mind this is FAT32 (case preserved, case insensitive) -
Study of the file system contents after the initial factory update completes shows the filename in-use was:
UPDATE~1.BIN
(the 8.3 format name of a long file name and no long file name found).
And that FAT-32 is not an inode based system, mounted into a file system tree that expects an inode based system -
Translation: The driver munges up the missing information during read/write of a file or directory name.
What you see is not always what is recorded on the media.
How that munging is done and what gets munged depends on what options where passed to the VFAT driver when the FAT file system was mounted.
In the case of USB storage viewed from the outside (USB cable) it gets a little bit more obscure, you are looking at the media through two drivers (plus whatever is on the PC end of the cable):
/mnt/us -> fuse driver -> /mnt/base-us -> VFAT driver -> media
**BUT** an uppercase, 8.3 format name using the characters from 7-bit ASCII **should** pass through that mess un-touched *in name* (the drivers will still fake up the ownership, permissions, and times).
Making directory names is cheap - -
Add "UPDATE~1.BIN" to the list of directory names your going to make in the root of USB storage.
- - - -
Which may just force the OTA updater to use: UPDATE~2.BIN (or UPDATE~?.BIN in its look-up. I haven't done any testing on if it can handle that situation).