Maybe my lawyer has a really old version of Word or something and he keeps sending me files in an old format that isn't supported as well.
I've also had a lot of files opened flawlessly by LibreOffice; it depends on how many features you're using. Maybe you're trading documents that aren't that complicated?
You see, it is the word processor for all the non-techie people out there. They have no idea how to properly use it (and pc's in general), so they blame Word for all their faults.
LibreOffice, on the other hand, has much more competent userbase (in average), and despite the lack of certain features LibreOffice has more positive image.
If there are no detailed Word error messages or diagnostics, perhaps you could ask your lawyer to send you a PDF or paper version, so you can tell if there are any differences.
I for one would be very attentive to the possibility of missing or incorrect information in legal documents...
One document went back and forth between Word and LibreOffice and the numbering was always screwed up. Instead of:
1. 2. 3.
...it would come in:
.1 .2 .3
No actual missing information. Just screwed up formatting.