Products don't stay in collections. I am struggling with this issue.

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hey guys,
I hope someone here can light me up with a solution.
I have 3 products in my store that get automatically not visible everyday.
It happens since ever, and i need to get in to the dashboard and tick them again in the "online store" to make them visible. It is really annoying and i have no idea why it is happening with just these 3 products.
I have already deleted the collection, and created a new one trying to see if it could fix it, but no success.

Any light there? 🤯