Navien NPE-240s-NG Suddenly 93 degrees versus 120

[Canadianeh]

Found this site searching google. My water heater is suddenly only kicking out 93 degrees versus 120 that its set at.

Haven't ever had a problem until today.

I noticed a lot of threads said the check valve could be the issue for Navien heaters.

1) Do you think this is the case? Not sure this model even has a check valve according to the manual?
3) Anything else I can try?

Thanks in advance! It's the NPE-240s-NG model.

 

[Breplum]

the S series has no check valve.
Error code?
Has to be run through a series of checks to see if it is reading flow accurately.
Ever descaled? that is a question we always ask, but only sometimes relevant.