The security of Internet of Things (IoT) devices is crucial to protect the vast amounts of data exposed due to their widespread adoption. Authentication is one of the key aspects of IoT security, but it becomes increasingly challenging, especially for resource-constrained devices that require lightweight and efficient solutions. Physical Unclonable Functions (PUFs) have emerged as a promising lightweight solution by using the unique physical properties of Integrated Circuits (ICs). Pseudo Liner Feedback Shift Register PUF (PLPUF) is one of the state-of-the-art implementations known for its flexibility in altering the challenge-response space by changing the activation duration. In this work, we demonstrate that selecting an appropriate activation duration for PLPUF is critical, as improper choices can compromise security. By analyzing the linear dependency between the responses of different PLPUF pairs, our results reveal that predictability can reach up to $96 \%$ when an unsuitable activation duration is chosen.