'Use custom bridges' radio button is not automatically selected when custom bridges are entered
The fourth screen of the Tor Browser's 'Configure' wizard gives the user the option of either using a standard set of bridges, or entering a set they have obtained elsewhere. These options are presented as radio buttons, and by default the 'Use provided bridges' button is selected.
If the user clicks on the box to enter custom bridges, the associated radio button is not automatically selected; if the user does not spot this or is not aware that they need to choose the second button, clicking 'Connect' will (probably?) not cause Tor Browser to try the bridges entered in the text box. Users may nevertheless think that the bridges they have entered actually were tried and found to be blocked/faulty/unreachable, when in reality it is the provided bridges that don't work.