Wrong kaddish

Hi,

After uva l'tzion in the morning Shacharit service, the chazan is supposed to recite a full kaddish. If a mourner doesn't realize that this kaddish is specific to the chazan, and he begins reciting his own kaddish, one should quietly, politely stop him.

(Rivivot Ephraim 1:111)

Have a great day,
Mordechai