I have a 3 pop city called Pasargadae with a 25/60 granary in the production queue (at normal speed) and am running slavery.
But. THe whip button will not allow me to whip it, it says that it requires 2 pop, which the city has spare, bit then states that max availiable is 1.

I am running BTS 3.17 with Solvers patch (0.19) the BUG MOD 3.0 build 945 on top of that.

See screenie and attached file if that is not enough.

You can only do up to half your population at any one time (rounded down), thus half of 3 is 1.5 and rounded down is 1. Been this way since vanilla as far as I know.

Thanks. Husyor, My mistake.