so, after testing this, i have determined this is a limit in onenote itself.
sucks

i created a new notebook,
i added sections one at a time and saved after each
it worked fine at 1,737,506k
it worked fine at 1,738,413k
it failed at 1,752,281
i then removed the last section to insure no corruption
i added a different section and saved
it failed at 1,761,487

so thats it, the limit is in onenote