I recently set up a screen unlock code. Later, I set the alarm clock.
When the alarm clock went off the turn-off-alarm screen overrides the unlock code screen, but the phone won't allow turning off the alarm till after unlocking the phone.
I had to hold in the power button and do a hard reset.
Bugs are best reported to the developer of the software having the issue.
For alarm clock issues like that you might want to also try adjusting the settings for notifications to not shown on the lock screen to allow for the unlocking procedure, or a different alarm app that can offer better functionality for your lock screen
I never had a issue with turning off an alarm on a Motorola phone when it was setup with a pass code. Granted it wasn't a DROID Turbo 2, but it was likely a similar situation.
I'm most definitely NOT a VZW employee. If a post answered your question, please mark it as the answer.