Diagnosis
This is a common mesh networking quirk called 'sticky client.' Your phone, laptop, or other device is clinging to the first point it connected to, even when a stronger signal is available. The router can suggest a switch, but the final decision is up to your device.
How to Fix It
You can't force it from the Nest, but you can encourage better behavior. 1) In the Google Home app, go to WiFi > Settings > Devices. Tap the problem device and see which point it's connected to. 2) The best fix is often to temporarily turn off the WiFi on that device for 10 seconds and turn it back on. It will usually grab the strongest signal from scratch. 3) For a more permanent help, ensure your points are placed too far apart. They should be within 1-2 rooms of each other for a strong backhaul signal.
If That Didn't Work
Some devices (especially older ones) are just bad at roaming. You can try forgetting your WiFi network on the device and re-joining it while standing next to the preferred point.
Heads Up
The 'Priority device' feature in the Home app doesn't fix this; it just reserves bandwidth. Also, having the same network name (SSID) for both 2.4GHz and 6GHz bands is recommended for Nest Wifi Pro, but it can contribute to this issue. It's still the best setup for most people, despite the occasional sticky client.