Hello @Forrje01
Do you mean the AX55 disconnects from the internet frequently ever since you connect the Chromecast to the 5G network? If that is the case, what if you disconnect the Chromecast from the network, will the AX55 connects to the internet stably?
Who is your ISP? Is the internet LED on the AX55 staying green or turning orange when it disconnects from the internet? Does it still get a valid IP address from the ISP modem?
When the issue happens, we would like to have the system log on the AX55, then the engineers may investigate further. Please email the system log to support with the subject [Forum ID 569822] Router keeps disconnecting, modem is fine, thank you.