Selecting two categories shows no results – each category on its own has results

Hello,

There’s a strange scenario where if I select two categories it shows no results even though there are results if you select each one separately. I tried to set the filter to AND and OR and it doesn’t make any difference.
The Categories have hierarchy: Clothing > T-Shirts
Products have both categories marked and T-Shirts is the primary term for both of them. Here are some screenshot to show the issue:

Checking child category works:

Checking parent category works:

Checking both of them shows no results:

Why is this happening?

Thanks

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