My iPhone disconnects from the Wi-Fi network frequently (or intermittently) when the screen is locked / in sleep mode (screen off). The connection drops after a short time (seconds to minutes), and it reconnects quickly upon unlocking the device or waking the screen. This causes delays in notifications, background app refreshes, and general instability.

The problem started immediately after I replaced my old ISP modem/router (which had separate SSIDs for 2.4 GHz and 5 GHz bands) with the TP-Link Deco M4 mesh system. With the old router (separate bands), the iPhone stayed connected reliably even when locked. Now, with the Deco M4 using a single combined SSID (band steering/Smart Connect enabled by default), the issue occurs consistently.

This affects my iPhone specifically (and possibly other iOS devices), while other devices (Android, laptops, etc.) seem more stable. The Deco units show white LED (online/no obvious errors), and internet works fine when the phone is unlocked/active.

Steps Already Tried (Troubleshooting Performed):

1. Disabled Assistência Wi-Fi (Wi-Fi Assist) on the iPhone: Settings > Cellular > Wi-Fi Assist (turned off).
2. Disabled Mesh Technology (or similar per-device option) specifically for my iPhone in the Deco App: More > Devices > Select iPhone > Turn off Mesh Technology/Fast Roaming/Connection Preference if available.
3. Disabled Fast Roaming globally in the Deco App: More > Advanced > Turn off Fast Roaming.
4. Disabled Beamforming globally (if the option was available): More > Advanced > Turn off Beamforming.
5. Confirmed no Low Power Mode active on iPhone during tests.
6. Did NOT create a Guest Network (as it would prevent my iPhone from accessing home smart lights/lamps that require the main network).
7. Forgot the Wi-Fi network on the iPhone and reconnected multiple times.
8. Checked for Deco firmware updates in the app and applied the latest available.
9. Tested while iPhone is charging (Wi-Fi stays more active, but issue persists when not charging).
10. Other iPhone settings tried: Temporarily disabled Private Wi-Fi Address on the Deco network (Settings > Wi-Fi > (i) next to network > Private Wi-Fi Address > Off).

None of the above steps resolved the issue. The disconnects continue when the screen locks.