When you say static IP I assume that is a static IP set on the mixer.
For what it’s worth I run my QU Pac set up with a static IP all the time and use a
5g WIFI connection with no problems. My routers are set up with a hidden SSID and the encryption turned off.
In my very brief attempt in using a 2.4g connection I would get more or less the same problems you are.
Same here. Hidden network, static IP address, and 5ghz every time. Also, once I started using the Apple Airport Express, the system worked as it should 99.9% of the time. Anything else has never brought me good results.