percentage not correct

[fkarg]

When reading a longer text, I noticed the progressBar showing progress at unlikely frequency. It sometimes even jumps about 20% at once. If you go back then, It'll show 1% left, but opening it it's back to 46% left or whatever it should be. But sometimes, it's jumping to those 1% that are left and is ignoring the other 45% or whatever you were missing from last time.