@Megawatt will know just by looking, but as far as these UK eyes can tell…. Something isn’t in the right place.
At a guess, because I don’t know which is the common terminal from here…. The reds would go in the common at each end, and the blacks are the travellers (pass wires or strappers over here) between switches.
One of those reds will be hot…. Be careful to isolate before working.
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