I noticed that by default .odt is not an allowed file upload. Where do you change the file types allowed for upload?
I think something like the following might help... this means you have to intercept the field in getCMSfields and also not that these are case sensitive.... please look at sapphire\forms\FileField.php for more info....
An alternative solution would be to add this line
File::$allowed_extensions = 'odt';
to your mysite/_config.php.
did you solve your issue?
do you have any problems linking or accessing the file once uploaded?