Thanks for the feedback! Sorry about your 5-star run :(
I agree completely - locked dice should not be rerolled, and vice versa. I actually think this is a UI issue - I'm guessing that you were using Sculpt Fate as this happened? For that ability, it made sense to me that the buttons used to lock the dice showed a closed padlock while the dice were unlocked (since you use the button to lock the die), but I totally get that it can be interpreted as "this die is now locked". It's probably even the most logical interpretation.
I'll definitely think about how to make this more clear in future versions. Thanks again!