What is the name of your state? Texas
Does the divorce decree become "void" in some way if someone breaks what was agreed to?
No. A huge percentage of divorce decrees are 'broken' in some way - often by mutual agreement.
If you feel that the other party has violated the agreement, you have various options:
1. Talk with them about it and ask them to comply.
2. If that fails, go to court to file for contempt.
(some divorce decrees require mediation before going back to court, as well).
3. Ignore it
If it's a minor issue, it may be better to let it go.