Client with some niggly networking issues but we didn’t have the router admin creds to diagnose them (new-ish client, yes we could have factory reset it but didn’t want to in case it made the issues worst). Obtained the router login details recently and found the router has the same IP address as the managed switch service provided by their serviced office. Not taking it for granted but that’d cause some weird issues along the lines of those we’re seeing.

IP address changed. We’ll keep monitoring.