How to replace the architrave switch?
Switches with four terminals are used for lights controlled by switches in three or more locations. Also for certain kinds of equipment where both hot wires are switched as opposed to just one.
To find out for sure you would need either the switch instructions or to conduct tests by taking a multimeter and measuring continuity between every combination and permutation of terminals taken two at a time. Repeat the tests with the switch in the other position.
If the switch is defective, it will require intuition that experienced electricians have to interpret the test results. (You don't need an electrician's license to have that intution.)
The disadvantages of crab apple trees. In summer, the apples are too sour to pick and eat. In winter the birds come and leave dropping all over the place.