Brilliant thank you Sven, I have updated my little storage measurement to include high memory usage processes so we should find something on our next visit.

Ideally we should not need swap so I assume we're not clearing our cache from memory and just have not noticed it yet.

Hopefully the cause ...

We have a RevPi in production and it's been running for 2 months now.
Recently our PLC has been failing to see the RevPi's heartbeat we setup using an output controlled by NodeRed.
Initial steps to diagnose were we could SSH and use RevPi Commander, but we could not access the web interface for ...