I'm glad you like the plugin 🙂
I think you just discovered a bug, as I was able to confirm the same behavior on my test environment. The recent version introduced the possibility to filter by the same custom field multiple times, but I guess I made a mistake somewhere. I'm going to investigate further and fix this for the upcoming update. Sorry about that.
For this purpose I rather recommend using the “Range Slider” type instead of the drop-down, as it was designed for this exact purpose. It's more compact and performant, as it does one “between” operation instead of two (more then, less then) when using drop-down values.Best,
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