Intermittent connection failures

When using my iPhone on my Wi-Fi network on Comcast in Seattle area, I occasionally get some mobile apps failing to access data, resulting in a blank page infinitely waiting to receive data. Being somewhat impatient in nature, I just immediately switch to Cellular Data and the problem goes away.

Being an experience engineer with lots of data networking expertise under my best, I would think. I could figure it out with the right tools and patience.

On the face of it, looks like a NAT/CGNAT issue, but I can't tell for sure if this is due to my home router (Eero) or Comcast CGNAT (which they introduced in my area).
The Eero thing does not expose any access to logs, and if I manage to somehow sniff the network I doubt I would be able to tell which NAT layer is at fault here.

Something tells me though it is more likely Comcast CGNAT rather than my home router NAT because the use patters in my house have not changed, and the number of concurrent connections is unlikely to exceed the NAT table size.

By the way, the two apps I noticed having these intermittent issues are X (formerly twitter) and Fidelity Investments.

Wonder if anyone observed similar issues.