This is the designed behavior since the earliest days of VaultWiki 3. If you use "thumb" or "frame", then you need to use "none" or "inline" in order to keep the file in the content flow. If you are using the File Browser to insert your attachment then "inline" should be the default selection.
Please double-check your FILE parameters.
I will leave this open for now because the designed behavior is not documented on Special:WikiCodeList (so treating this as a documentation issue).