I guess you mean that you do your workout sets as prescribed and when you finish the app says Attention, your 1RM has gone down, etc, correct?  I wanted to ask this as well, why it happens.  I guess, it always takes into account the last 3 workouts perhaps?  I was curious about this one myself and actually was wondering if this is the case or an actual mistake in what is suggested...

I see!  Good to know anyway, until it's fixed!

What happens when a few (wrongly entered) sets or whole sessions are deleted?  Will the corresponding exercise(s) be updated?  Thanks!

OK, so I go to Exercises --> Add my own --> I name the exercise --> It asks for a 6RM --> I click on Cancel (tap outside doesn't do anything) --> I go back to Workouts --> More & Edit on the Workout I want to enter the new exercise --> I 'open' the new exercise to enter it --> I save the workout --> I click on this workout and click on the new exercise --> It asks for the previous 3 sessions (weight and reps). 

I typed these as I was going through the steps one by one, just to be sure. I've got iPhone 5s, so not sure why it does that to me, lol!

This came up when I entered a new exercise, but I actually wanted to test the 6RM next time I was in the gym...

I hope this is more clear now!

Cheers!