I had the problem described above and tried the solution described above. While it did solve the problem of my contacts being associated with the wrong SMS threads, it also seems like it had the side effect of erasing all images from all the text threads. I assume that was likely the "delete storage" portion, but I'm honestly not sure. I still have my seedvault backup (as well as my previous device, which I have not wiped yet). Is there any way to restore the images?
I tried restoring from seedvault again and selecting only "SMS test messages" to restore, but that didn't seem to work (and "SMS text messages" entry was shown as something like 400k, so that does suggest it's only the text portion of things). Obviously the images would technically be MMS messages, but I didn't see that explicitly referred to.