Riff of the day variable training tempo
I am not sure who thought that it will be a good idea to change the tempo of the riff during the playthrough as you're learning it and make the changes quite aggressive as well, but I am sure they're a product manager and they have never played guitar.
It takes me from "I can comfortable" to "I cannot follow at all", without any discussion. It is frustrating. It shouldn't increase the tempo during a playthrough. It should ONLY increase the tempo after you finished the riff at the current speed without a single mistake at least 3 times.