There are several factors that may be causing the issue and from what I have found they are all pilot error.
1- When the plane starts out on scramble mission the tail wheel is turned slightly so if you are in cockpit view and lock your tail wheel, the plane will turn to the left. You need to pull the plane forward a bit and the tail wheel will straighten out. Then you can lock it.
2- When you start your engines, after starting the second engine make sure you have hit the key for " Select all engines" or only one will power up and you will pull to one side. You can check to make sure both are powering up by looking at the RPM gauges in the cockpit. Top two center. If both are moving then you have selected both engines.
3- If your throttle is not at zero % when you start a scramble mission and then you back it to zero then start engines, sometimes the game still reads it at a powered throttle and the plane will turn.
4- If you have trim on your stick and it is not zeroed out then that can cause pull as well.
As CWatson said, I tested in both 4.10 and 4.12 and I made the above mistakes at fiirst and then after correcting them, pilot error, the plane, both versions, will take off correctly.