Dumbells are not barbells.
Dumbells also allow you to lift safely because the weakest link in your kinetic chain is the limiting factor. With HS machines, that's not the case.
Youre wrong to think that HS machines are less likely to cause injury than dumbells. That may be true if youre talking about direct injuries that occur in the gym, but using HS machines on already unbalanced muscles can further weaken the weakest links, you see where this is going.
And who said the OP had an injury in the first place? A muscle/strength imbalance is definitely not an injury. But it can become one if not addressed.
Trust me when I say this. If you have a lagging muscle group, the last thing you want to do is make a certain movement easier. HS machines should be used by people who are keen to proper lifting motions. This is learned through the use of free weights.