Shiverz

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Also I know there is the argument that in real, official tests you can't restart. However I find Khan Academy's course challenges a place more to practice your skill sets rather than to actually do...

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2. Technical Issues and Workarounds
3. Courses disappeared from dashboard

Same. For me it was my physics course. I dunno where it went, but when I went and looked, the whole course was removed and replaced with another course that I didn't have mastery on.