script – Miniscript walkthrough for 3of4 multi-signature converted to 2of4 where only 2 specific keys can be used.

I was trying to write this script (miniscript):

or(multi(3,pk(key_1),pk(key_2),pk(key_3),pk(key_4)),and(previous(12960),multi(2,pk(key_3),pk(key_4))))

Here it is a 3of4 multi-signature that changes to 2of4 (only keys 3 and 4) after 90 days.

A “compilation error” occurs in bitcoin.sipa.be/miniscript/.

I also wrote: or(9@thresh(3,pk(key_1),pk(key_2),pk(key_3),pk(key_4)),and(older(12960),thresh(2,pk(key_3) ), pk(key_4))))

But I get a “duplicate key” error.

What on earth am I doing wrong?

Also, what does correct code look like?