Timer not always working

[Bailea]

Currently using preset timers. I found that at night sometimes my timer will not go off. At first I thought i must have been waking up and turning it off without realizing but the other night my husband and I both set timers on our phones. His was set to go off around the same time as mine but neither timer went off. When you set the timer it's counting down and says it will go off at blah blah time and I'll go to sleep and I'll wake up after when the timer is supposed to go off and it's no longer set (like it went off) but I never turned it off and my phone doesn't reflect a count down showing it went off but was never turned off by me. Most of the time it works but randomly it doesn't. 

[GoanGeek]

Hi and Welcome.

Just to clarify.

I hope you are not confusing Timer with Alarm clocks ?