This kind of problem can repeat at any time, because this is a whole class of different problems, that simply have similar superficial manifestation, but different internal causes, in an incredibly complex machinery of general-purpose word processing witchcraft, multiplied by magic of conversion during importing/exporting of external file formats.
And I keep fixing documents here because of two reasons: (1) I know how to do that (and I don’t hide the knowledge, but it’s really technical, so the times when I explained it, mostly didn’t help anyone); and (2) sometimes that allows to build understanding of the currently seen problem, to find a reproducer and then to fix it. If the problem happens, I try to do what I can to help people by things that I can do best (and I don’t feel tired of doing just that).
The problem usually happens in LibreOffice at export to DOCX time. It’s usually not the other party with MS Office. As said, yes, you won’t have an insurance that this won’t happen. But having your data in ODT (and only creating copies in DOCX) would generally safeguard you from data loss (but not from time waste when this happens, sure).