KH Guardian Issues - Reset & PH off

[Electric Corals]

Hello all I have been running a KH Guardian for 3 months, it was bought new. Recently it has been stopping during the standby countdown usually in the 90s-100s for a 120min timer. I did rest for a 90 standby time, seemed to run once okay, then it also had the failure in the 60s and reset the timer. It is always accompanied with a "BONK" sound.

Additionally PH probe read 5 - my handheld reader (calibrated) reads 8.2. Brand new, only been ran for 3 months.

 

[Electric Corals]

Bump* or anyone seen any good forms for this?