Pencil tool automatically changes color inconsistently

The Pencil tool is changing colors automatically and inconsistently without me changing any settings.
Sometimes it draws in white, sometimes in black, and the behavior seems random. It also doesn't reliably detect the background color.

Steps to reproduce:
1. Select the Pencil tool (Shift + P).
2. Start drawing on different backgrounds (black, white, colors, frames).
3. Observe that the stroke color changes between white and black automatically.

Expected behavior: Pencil should consistently use a color that has enough contrast with the background, or stay the same color as set by the user.

Actual behavior: The Pencil tool switches between different colors randomly, even on the same background, without any change in settings.

Why this is a problem: It interrupts workflow while sketching or wireframing. I have to constantly check and manually reset the color.

Feature / Improvement request:
Improve automatic contrast detection for the Pencil tool.
Add an option to disable automatic color switching.
Or allow locking the Pencil tool to a fixed stroke color.
A more predictable Pencil experience would greatly improve usability. Thanks!