Need help, edited XML, still cannot open file

Hi,

When I reopened the file, it could not be opened, citing format error discovered at row, column. I did a search and found help in this forum which I tried. I am using Ubuntu 14.04 and LibreOffice btw. I unzipped and tried editing the XML at column mentioned. Saved it and zipped back using command lines in ubuntu. When I open back the file, it said General input output error. And a google search on that didnt help as well. So I performed the same thing on non-problem file, unzip, no editing the XML, zip back and reopened. Surprisingly, I got same error. So it's not XML editing problem but something else. I might have errored in the XML editing but in second case, I did not edit the XML at all. I then updated the apt to get updated software but still same errors. Lastly, my backup file dated 2 weeks ago was decided to be used. Unfortunately, after saving that file itself gave format error discovered again. So I have no more backup other than here. Hopefully someone within same time zone or not sleeping yet could help me on this. It's urgent. Required for me to present in 3 hours. Please help me fix the file?

Please help. 

I didn't find the right solution from the Internet. References:- 
https://forum.openoffice.org/en/forum/viewtopic.php?f=5&t=86509
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Thanks!