Boyle was belting out "O Holy Night" -- when she began coughing and backed away from the mic ... then asked the producer if she could start over ... all while the cameras continued to roll.
After several awkward seconds, Whoopi and Sherri swooped in and bailed her out.
Producers tell us Boyle will retape her performance for the West Coast.
More Susan Boyle
- Susan Boyle Appearance on 'DWTS' -- Cancelled!
- Susan Boyle -- Screw 'Talent', I'm Going 'Dancing'
- Susan Boyle Sings 'Perfect Day'
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