Noritz tankless heater no fire

[griffisfarms]

I have a 12 year old Noritz tankless lp water heater. Flush with vinegar every 6 months. Within last several months, have had it fail to fire. Installer troubleshot and did not find anything wrong. Heres what we know: After a long shower, the next person gets in and water wont heat. If breaker is turned off and on while water is running, unit will fire and all is good. Filter clean. Flame rod clean. Lp pressure confirmed good. Could my ignitor be getting weak? What should I look for?

 

[Geofd]

I'm not familiar with those units but have you tried their tech services¿????,what did your installer say about the ignitor???