I haven't heard of the issue regarding missing notes. That shouldn't happen. If you notice anything about when and how it happens, please let us know.
We don't have an easy way to see what was wrong, other than if you are using the lesson scheduling, you can sort the notes based on how far they are into the lesson schedule (just click on the column header with the pie charts).
We will be adding flagging of notes soon, and other ways to see which notes were wrong last time you studied. These options will be in version 2.0, which is a few months away.
Same thing for me.
On my ipod lessons repeat wrong notes but doesn't repeat forever if
it's always marked wrong. I think it repeats not more than 7 times
a wrong card but i don't know the exact value. I tried all the
settings, now i think something must be fixed... I can film my
settings and the issue if you want...