Tags Lost

I work in a library and use Acrobat to tag files for visually-impaired students. Files are supplied by publishers "as is", so returning to the source document isn't an option.
 
I recently upgraded from Acrobat 8 Pro to Acrobat X Pro (running version 10.0.3, which is not listed in the drop-down box when posting this comment). I'm having problems saving changes to the tag tree. I save my work regularly and everything looks OK when I close the file, but when I next open it the changes are jumbled up and sometimes tags are duplicated. I thought I'd solved this by using "save as" before exiting (the renamed file was usually OK even if the original had been corrupted), but now I randomly get an error message when I hit the "save" button, along the lines of "the document could not be saved. There was an error reading the document (23)". The "save as" dialogue box then appears. Sometimes I was able to save the file (with changes) under a new name, but twice I got the dreaded "Acrobat has encountered an error and needs to close" - followed on the last occasion by "Microsoft Visual C++ runtime error".When this happened, I not only lost my last changes but also some tags. They can no longer be found in the tag tree, although they still show up in the reading order panel and TORT highlights the text on the offending pages as if it is tagged OK.
 
Can anyone help??? I'm seriously contemplating reverting to Acrobat 8.