Android apps extremely slow and often time out when device is connected to xFi Advanced Gateway (XB6)

I have 2 android devices - a Galaxy S10 and an Nvidia Shield.

Android apps - especially streaming apps such as HBO Max, Sling, Disney+Hotstar - always take forever (>30 seconds) to load when my device is connected to the router provided by Xfinity. Even the video will be extremely slow to start but seek times are minimal once the video actually starts playing.

The speed test results are usually >300 Mbps and apps such Netflix, YouTube, and Prime video work perfectly.

Furthermore, I notice absolutely no issues when my devices are connected to LTE (T-Mobile) or the "xfinitywifi" public hotspot. (which rules out system webview being the culprit)

Strangely, only android apps seem to be impacted since the websites and iPhone apps of these services do not seem to have this problem.

I am led to believe the xFi Advanced Gateway has a bug and/or Xfinity has a weird/buggy algorithm to throttle some of these services.

Has anyone else encountered something similar?