I have never seen that error before in WP in general. This isn’t something I have any other reports of, and it’s not anything I’m able to reproduce on my own test servers, so it must be something unique going on there.
We can troubleshoot this directly, but we would need you to submit an order for premium support in order for us to do that.
That can get expensive, so I would recommend temporarily disabling other plugins to see if the problem goes away. Also switch to a basic theme if you need to. The idea is to eliminate as many pieces as possible to see if the problem goes away.
If so, then you can start re-enabling things one at a time until the problem comes back. Then you’ll know the culprit, and at that point we could try to reproduce the problem and get it worked out on our end.