Clock app, no alarm bug (iPhone 6; iOS 8 to 8.3)

Does anyone else have this problem? This bug has been plaguing random iPhones since iPhone 4 or maybe earlier.

Bug:

• Set an alarm or a timer in the clock app
• Alarm/timer either
  1. goes off and shows the visual alert on the screen, but makes no sound. In some cases it may or may not vibrate.
  2. does not go off at all, or goes off for half a second then stops. Either way the alarm turns itself off.
  3. goes off normally.
• I get behaviours 2 and 3 for alarms, and all three behaviours for timers. Getting behaviour 3 is not often though.
• The bug is unpredictable and I am unable to reproduce it. When I try to reproduce it, the alarms and timers go off normally. When I need to actually use the functions, they bug out.
• My ringer, speaker, volume, vibration, are perfectly fine and properly configured.

Attempts to fix bug that did not work:

• Delete all alarms and remake them.
• Delete all alarms and make new ones every time an alarm is needed. Do not reuse alarms using the switches.
• Close every other app and keep the Clock app the only one running in the app switcher.
• Close every other app and keep the Clock app on the screen and have auto lock off.
• Reset firmware to factory settings via Reset in the Settings app.
• Restore firmware to latest via iTunes.

Questions:

• Has anyone else encountered this bug on an iPhone 6? I know it's been around before, but even on the latest device?
• Would I be able to get a free exchange from an Apple Store, given that this bug is not reproducible? I bought this device 8 months ago.