Something trying to access beyond end of FAT partition

I have a USB GPS with internal flash memory formatted as FAT-16 used for storing logs. But when I try to retrieve the logs, I cannot actually open the files properly. Pluma complains that it cannot detect the encoding. Vim opens the file just fine but the last ~10% of the file or so is gibberish.

dmesg | tail shows
Code:[496127.507796] sdb1: rw=0, want=15329, limit=15312
[496127.507801] Buffer I/O error on dev sdb1, logical block 15328, async page read
[496127.507805] attempt to access beyond end of device
[496127.507810] sdb1: rw=0, want=15332, limit=15312
[496127.507815] Buffer I/O error on dev sdb1, logical block 15331, async page read
[496127.507819] attempt to access beyond end of device
[496127.507824] sdb1: rw=0, want=15333, limit=15312
[496127.507828] Buffer I/O error on dev sdb1, logical block 15332, async page read
[496127.507909] attempt to access beyond end of device
[496127.507915] sdb1: rw=0, want=15418, limit=15312And fdisk shows this:
Quote:

Disk /dev/sdb: 7.5 MiB, 7839744 bytes, 15312 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disklabel type: dos Disk identifier: 0x00000000 Device Boot Start End Sectors Size Id Type /dev/sdb1 63 15311 15249 7.5M 4 FAT16 <32M

It looks to me like the partition fits where it should, so where is the problem? Does the GPS in firmware think it has more storage than it does? These log files are only several hundred KB's with a few MB's free, so I'm not even close to being full. Any ideas?