2007 Maxxus watchdog error

[wbilotta]

I have a 2007 Maxxus hot tub and it randomly goes into watchdog mode.  The incoming power is fine (I'm an electrician).  I ohm'd the heater sensor and temp sensor.  Temp sensor was ~20K which was close to water temp, the heater sensor was ~14K which is off my temp/resistance reference chart so I replaced it.

Tub fired up, ran for a while then I heard the contactor click a few times and then it was back into watchdog mode.  I've checked everything I can inside the control panel as far as connections/fuses/etc.

The two main capacitors are not bulged and the flow switch was replaced earlier in the year.

Anything else I can check ?

[wbilotta]

UPDATE: Now when I turn the power on I get differing amount of characters/lines on the display.  Before I would get either the    ---- or the tub would work for a little while then go into watchdog mode.

UPDATE#2: Now when I turn it on the entire LCD display lights up and has a very fast flicker.

[Jacuzzi Jim]

  Bad high limit possibly, doubt full, is that what your calling the heater sensor?      Flow switch again maybe, loose connection on board from sensors??  Worse case bad board, but the fact it runs awhile wouldn't make sense..    Circ pump failing intermittently.

  Kill the power, remove the filters, power back on and let it run without the filters in it, and see what happens. 

[wbilotta]

  Bad high limit possibly, doubt full, is that what your calling the heater sensor?      Flow switch again maybe, loose connection on board from sensors??  Worse case bad board, but the fact it runs awhile wouldn't make sense..    Circ pump failing intermittently.

  Kill the power, remove the filters, power back on and let it run without the filters in it, and see what happens.

Yes, the sensor located in the heater well.  I pulled and reconnected the sensor strip several times.  When I went out the display just had ---- showing, turned the power off, pulled the filter, turned the power back on and now every segment on the display is lit up. 

Bad capacitors ?