What is the ruling on a wife breaking an oath of divorce, if the husband does not recall the exact wording of the oath, but his intention was to restrict communication for a specific period and not absolutely?

If you intended by your oath to prevent your wife from speaking to her mother temporarily until a problem is resolved, and not as a permanent ban, then you have not broken your oath, and no divorce occurs if she speaks to her mother after the problem has ended. What matters in oaths is the intention of the one swearing, as long as the wording can accommodate it. We remind you that the mother's right is great and showing dutifulness to her is obligatory, even if she commits wrong. The lawful oath is by Allah Almighty, not by divorce.