Hi Michael,
I have the same trouble with my emmc. Thought it is an hardwarre issue (till today) and bought a new one. Today, I did an apt update && apt upgrade on my Odroid C2 that works as a headless Server. During the update, I got the following entry in the syslog:
[1192245.968722] EXT4-fs error (device mmcblk0p1): ext4_find_dest_de:1639: inode #43529: block 12032: comm dpkg: bad entry in directory: rec_len % 4 != 0 - offset=0(0), inode=8213, rec_len=4097, name_len=0
[1192245.985979] Aborting journal on device mmcblk0p1-8.
[1192245.991429] EXT4-fs (mmcblk0p1): Remounting filesystem read-only
[1192245.997249] EXT4-fs error (device mmcblk0p1) in ext4_evict_inode:241: Journal has aborted
[1192246.007682] EXT4-fs error (device mmcblk0p1) in ext4_create:2249: IO failure
When I compare it with your log entry, it looks like the same Problem. Hope, there will be a fix soon.