In the last test, Handscomb tried at least 3 different techniques (his standard, an exaggerated move to the off and no movement whatsoever) and looked progressively worse with each one
That's hardly surprising as it's almost impossible to change mid-innings
Anyway, to my eyes, he has 2 issues
Firstly, his starting position is so far behind the popping crease that it encourage the bowlers to bowl fuller which promotes movement
Secondly, his weight distribution seems to be primarily on the back foot which restricts his ability to get a meaningful stride in when he does come forward.
As a consequence, he is a sitting duck for quality seam bowlers like Broad and Anderson
If he is going to make a change to the technique that got him there, then a really simple one might be to take up his stance in a relatively "normal" position (i.e. back foot round about the popping crease)
In doing so, the bowlers would at least be forced to bring their length back a touch, potentially resulting in less movement and playing to his strengths
Also, when playing off the front foot, he would be further down the pitch which also negates movement and can create doubt in the mind of the umpire