Some apps don't work on wi-fi, but work on mobile data

I recently bought Nokia 6.1 Plus. It's running Android 8.0.1 September security patch.

Ever since I bought this phone, some apps have not been working with my wi-fi connection, specifically, Quora and Netflix. All other apps work fine, I am able to browse internet, make WhatsApp video calls, watch YouTube and Hotstar videos, etc.

I looked for solutions online and tried the following

• Disable IPv6 on my router - it didn't seem to be enabled at all.
• Forget wi-fi network - tried. Tried changing SSID on router, resetting network settings on my phone, rebooted router, disabled wi-fi security
• Disabled battery optimisation for these apps
• Background data is not restricted for these apps. There's nothing in permissions to say that wi-fi access could be restricted

The moment I switch off wi-fi and connect to mobile data, the apps start working. They don't work only on wi-fi. I have tried with other wi-fi connections as well and gotten the same result.

Can't seem to think what else I can try. I'm out of ideas.