That makes sense since the regulator is providing the same output voltage. The will be split evenly then and the smaller pack will deplete faster. If there are no regulators involved the two packs will need to be at the same voltage (Ohm's Law) and they will reach discharge at the same point.

In the OP's case I doubt he has a servo messed up or anything. I still think that the Fromeco regulator is not acting right since it is not apparently passing the load to its battery as it should. The other pack/regulator is doing all the work. The load should be split evenly, but for some reason the Fromeco regulator is not doing its job.