Here is the link to the Roar of the Pelican thread.
This was one of the first incidents reported on CPF.
Make sure the batteries in your multi cell CR123 light are at the same state of charge.
This can be done by using a tester like the ZTS tester, measuring the cell voltage under some kind of load, or recycling cells after they have been partially used to avoid mixing up a partially used cell with a new cell.
It is also a good idea to use a quality cell.