my checkout to be very, very slow.

I know the program will filter the order if the item is in the order. But he caused my checkout to be very, very slow.
Is there any way to stop this preset, I am manually splitting the order, thanks
Or is there any other function causing it? Can you tell me?

Order split settings default:
Default (If any of the following product items are found in the order, the split will be performed. Therefore, each item in the order will be added to a separate order.)