LTC6993

I am using an LTC6993-3 timer chip and I am using it to generate a positive output pulse of approximately 27 seconds.  It is triggered from a high to low transition on the trigger pin and this transition is produced by a comparator.  This device is non-retriggerable.  My set resistor is 649 KΩ and my top DIV resistor is 1 MΩ and the bottom DIV resistor is 887 KΩ.  Most of the time i get the 27 second pulse out but sometimes the positive out is so short in time that it is hard to find.  Is there a time between the trigger signal being received and the output changing states during which the LTC6993-3 trigger signal can be overridden?  Does anyone have a suggestion for what could be causing this?  The environment is very noisy and I am having the board relayed out to try to address the noise issues.

Thank you for any help anyone can provide.