Mesa 7i97t

flyingbrick wrote:

 The 7I97T is powered by a Mean Well 5V PSU with no earth connection.

Must have earth connection, on all power supplies.

Thanks all. Ground the PSU but this wasn't the cause

I should have known this but turns out the pi cannot use Ethernet and wifi reliably at the same time

You can try using a USB WiFi dongle, but that is also "hit or miss", so it might work fine or might not work at all or might work intermittently.
I've had very good luck with USB to LAN adapters, so far out of over 10, all have worked fine for connecting to Mesa boards.
This also gives you 2 options for Mesa so you can test what works better for you.