The little 2-pin connectors that Aquacomputer uses for the temp sensors are kind of finnicky. I have had them not quite make contact and I have also had them pull out. I also have an Aquacomputer
#53026 with a cracked 2-pin connector. This caused enough play that the sensor connection was intermittent. If you have not already done so, I suggest carefully inspecting the sensor connectors and how they plug into the Octo. Make sure they are fully seated and not cracked or damaged in any way. Good luck!