Disappearing conversation

So for the last three to four days a dm conversation I have with someone has been disappearing entirely from my dm box any time I go off Instagram for more than a couple of hours. What’s strange is they’ve noticed it too on their end.

What’s stranger is that I’ll just pull up their page and press the “message” button and the entire conversation will reappear. They’ve experienced this as well.

Anyone know why this is happening?