I was working on a larger form with 6 tabs, columns, and a few conditionals posting to a custom table. I added some custom_html fields to help with spacing. After I did, I wasn't able to save ANY data.
I started commenting out fields and sections until I got it to start saving again. There were a couple culprits for my install. If I put the custom_html field, nothing would save. I worked my way down the form. I had to comment out all the custom_html and almost all of the heading fields. I've made some CSS changes to work around the spacing. I still need a couple headings, but I will look at other workarounds for the time being.
I tried this on two separate installs. One as a multisite and the other is brand new install with nothing else. This appears to be a bug. I've not dug in the code to troubleshoot yet.
I can post the code, but it is fairly large.
Thanks,
-Todd