iPhone 17 Pro Wi-Fi bug or router mismatch?

I recently picked up an iPhone 17 Pro and I’m running into some really frustrating Wi-Fi issues. Here’s what’s happening:

• When I run back-to-back speed tests seconds apart, I get drastically different results (e.g. 200 Mbps down → 40 Mbps down).
• During FaceTime calls, Safari pages sometimes won’t load at all. The phone seems to choke if I try to do both at once.
• Cellular speed tests are much faster and more stable than Wi-Fi, which feels backwards.
• Remote diagnostics from Apple came back “fine,” and the Apple Store told me my “old modem” might be the cause.

My suspicion: my home router is a bit older and doesn’t support Wi-Fi 7. Could it be that the iPhone 17 Pro’s new N1 wireless chip isn’t playing nice with older Wi-Fi standards (Wi-Fi 5/6), causing these stability problems?

Has anyone else run into this? If you’re using an iPhone 17 Pro with a non-Wi-Fi 7 router, do you see the same speed test swings and FaceTime/Safari issues? Or is this more likely just the broader iPhone 17 Wi-Fi bug Apple is working on in iOS 26.1?

Would love to hear if this is router compatibility or a phone issue. Thanks!