In addition, if he doesn't sue, there is no need to take the initiative to void it. After all, invalidation costs money.
The best solution is that you are in normal production. When the other party sends you a lawyer's letter saying that you are infringing (of course, the other party may be guilty and don't care at all), you send a letter to the other party, which shows that this is the existing design according to the evidence. Then. . . . . Patents continue to exist, and both you and the other party produce them, scaring the third party with patents that are actually useless. . . .