Crist,
The short answer: THEY ARE VERY RELIABLE! :-)
I'm sorry to hear you had a problem, glad that it happened during "test" ;-)
I have over 250 flights on JMP timers. In the beginning I had three of them all with different programs, for the 1st 25 flights. This allowed me to make quick changes at the field. After the 1st 25 flights, I had the setup and prop where it was perfect for me. Since then I have used the same JMP timer for 225 flights with NO problems. Will Moore has hundreds of trouble free flights on his JMP timers, as do others.
I would suggest that you send it back to where you bought it. Jean-Marie is a nice guy, you may get an exchange?