Thanks a lot for your response. My problem is actually that clicks aren't registering to move the boulder - https://www.screenr.com/OtJN. Shift is of course always depressed, and you can see the clicks register but not plant the waypoint flag. Maybe it's a computer issue.
I haven't ever seen such issue. It really looks like the shift button doesn't work properly (computer thinks it's not pressed). I'll add another boulder control button tomorrow, but until that... Try these steps.
1. Try using second shift button.
2. Open notepad, hold shift button, and type 100-150 letters, and check whether it works or not.
I've watched the chapter 7 challenge walkthrough and I can't replicate it, the boulder takes about a second to respond whether I click once or lots of times...
The boulder has inertia, so you need to target it a bit ahead. Also you don't need to be 100% accurate. Just try to hit as many shielders as you can. And all those special units are needed to be destroyed before they come too close. And also you can slow em down using gas mine (it wasn't shown in the video).
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I haven't ever seen such issue. It really looks like the shift button doesn't work properly (computer thinks it's not pressed). I'll add another boulder control button tomorrow, but until that... Try these steps. 1. Try using second shift button. 2. Open notepad, hold shift button, and type 100-150 letters, and check whether it works or not.