You're right. It's a bummer because I'm pretty crazy about that. I'd like to be able to see if text messaging backup actually works. I did a reset and I was able to upload all of my texts. I think this texting backup needs a little bit more work.
I had the Error 0x80181548 when trying to manually backup Lumia 920.
Turning off the backup in settings and doing a shutdown/restart and turning the backup back on worked for me.