A key labelled with both an F-number and a media symbol can send different commands depending on the keyboard's current mode. If an application shortcut suddenly changes the volume or brightness, check that mode before rewriting all your shortcuts.

Separate the key from the application

Pick a harmless shortcut in an application you know, using a disposable document if necessary. Record what the key does by itself and what it does with the keyboard's documented Fn modifier. Avoid testing combinations that could close unsaved work or trigger a send action.

Look up the exact keyboard model's function-key control. Logitech's MX Keys S guide, for example, documents Fn plus Esc as a switch between media keys and F-keys, with media access as the default. Other keyboards may use a different combination, a dedicated lock key or a firmware setting.

Do not assume that a small padlock symbol means the same thing on every product. Use the model guide to distinguish function lock from a computer lock command.

Change the mode, then repeat the test

Apply the supported mode switch once and repeat the same harmless shortcut. Check both the application's F-key action and a media function you use regularly. A successful change should make the relationship between the two predictable.

If only one application still behaves differently, inspect that application's shortcut configuration or the keyboard utility's app-specific profile. If letters and punctuation are wrong as well, that points to another setting such as the input layout; changing function-key mode will not resolve it.

Keep a brief note of the accepted mode on a shared workstation. Someone who expects direct media controls may accidentally reverse the change while trying to recover a shortcut.

There is usually no reason to install a new driver or remap every key merely because the dual-purpose row is in the other mode. Confirming the mode first preserves familiar shortcuts and gives you a clear observation if further diagnosis is needed.

Sources: Logitech MX Keys S function-key mode.