i think that on your motherboard slots 1 and 2 are the same channel 1, so when you connect those modules in those slots the system handles them ith the speed of the slowest module and the timings of the slowest module, so it gives you 16gbs single channel
when you use channel 1 and 3 it tries to do dual chanel and fails because each module has different settings
try to use slots 2 and 4, instead of 1 and 3, see if that boots and gives you dual channel
the reason to try 2 and 4 is because on some motherboards slot 2 and 4 are the first slots on each channel, contrary to the logic that tells you that 1 and 3 should be the first ones, some motherboards are like this, my gigabyte is like this
if it gives you dual channel it will be at the speed and timings of the slowest module