This question is related to this resolved thread.
We want to share the solution we found, in case someone else is struggling to find a reason for the same issue.
We were unable to save snippets with script tags in them - every time we attempted to save it, it would re-direct to the website’s home page without saving it.
As we couldn’t find a reason, we reported it as a bug here.
We also weren’t able to save publish form layouts, which led us to the above forum thread.
Adding
SecFilterScanPOST Offto the .htaccess file fixed both the snippet and the publish form issues.
Unfortunately, it looks like it isn’t possible for EE to produce an error message for these instances.