Repeat the lessons until you reach at least 97% accuracy without hesitating
That's one error in 33, which seems fair.
A seemingly small increase of 1pp to 98% means you need 50% more correct strokes per error. I tried doing this but it's a bit frustrating. Maybe it's even having the wrong effect on the training (i.e., I make more errors out of frustration).
Is 98% too high?