Mixture of a Strong Acid and Weak Acid vs.  The Strong Base or a Weak Base:

Within this curve there are two break points. A first break point corresponds to the neutralization of strong acid. When the strong acid has been fully neutralized just then the weak acid begins neutralizing. The second break point corresponds to the neutralization of weak acid and after in which the conductance increases because of the excess of OH^- ions within case of a strong base as the titrant.

Therefore, while the titrant is a weak base, it remains almost constant after the end points same to Figure.

Figure Conductometric titration of  a mixture of a strong acid (HCl) and a weak acid (CH₃COOH) vs. a strong base (NaOH) or a weak base (NH₄OH)