Hex motor not getting power at the same time

We are a rookie FTC team.
We are using block programming and connected two Core Hex motors to the Hub in port 0 and 1.
When we use the “Dual” mode under actuators in autonomous mode, to provide them power of 0.5 say for 3 sec, the motor in port 0 starts first and port 1 lags it (though we are using Dual option)
Essentially, with this, the robot doesn’t move in a straight part, it first turns because of the power in one core hex and then goes straight.
Same thing happens when we do a backward move.
Any help to synchronize to give power to both the motors at the same time.