DIAGNOSIS This is usually "client steering" or "roaming" not working perfectly. Your device (laptop, phone) is being stubborn and holding onto the first node it connected to, even when a much better signal is available.
FIX First, we can tweak the mesh settings. In the Linksys app, go to the Mesh Network section and select the specific node that devices are having trouble leaving. Look for an option called "Node Steering" or "Client Steering." Make sure it's enabled. This tells the nodes to proactively encourage devices to switch to the best signal. Also, check for "Fast Roaming" (802.11k/v/r) settings and ensure they are turned ON. These protocols help devices roam more seamlessly between nodes.
IF THAT DIDN'T WORK The problem might be on your device side, not the router. On the problematic device (like an iPhone), go to Wi-Fi settings, tap the (i) next to your network, and turn OFF "Private Wi-Fi Address" (this is a MAC randomization feature). Sometimes this confuses the router's ability to track and steer the device properly. You can turn it back on later for security if needed, but test with it off first.
HEADS UP Some older devices just have bad Wi-Fi antennas or drivers and will always be poor at roaming. The mesh system can only suggest a switch; the final decision is up to your phone or laptop. If one particular old device is the only troublemaker, the issue is likely with that gadget, not your Atlas system.