Price changes after the order is made

Hello,
Prices of some products keep changing. I lost a lot of money due to this problem.
Here is an example:
This product was listed for $15.99, but after the first order, the price dropped to $5.77, which is even less than the Aliexpress price of $7.25! I didn’t notice that until the orders were processed!
https://monalisamedical.com/product/mess-free-cupcake-pancake-maker/

I synched all products imported, then the price went up to $25.99! And after one order is placed at this price, the price went back to $5.77!
I did another synch, and currently the price is at $15.99
In the plugin settings, I went to Product Sync, and under Sync Price option, I added this product to the Exclude Products, hoping the current $15.99 won’t change.
This problem happened with a couple of other products. The problem is resolved when I sync all imported items.

Please help.