Extremely long pen lines are drawn incorrectly on certain iOS devices

[RexScratch]

Expected Behavior

Extremely long pen lines (those that are hundreds of thousands of pixels long) should be drawn correctly on all devices.

Actual Behavior

Extremely long pen lines are not drawn correctly on the two iOS devices I tested. The Windows laptop drew these lines as expected.

Laptop on Windows 10 2004 with i7-1065G7 processor and integrated graphics on Edge 84.0.522.50:

iPhone XS on iOS 13.5.1 with Apple A12 processor and graphics on mobile Safari:

iPad (6th gen) on iPadOS 13.5.1 with Apple A10 processor and graphics on mobile Safari:

Steps to Reproduce

Draw a pen line that is over ~100,000 pixels long.
Here is a project screenshotted above: https://llk.github.io/scratch-gui/develop/#415405297

Operating System and Browser

iOS 13.5.1 Safari
iPadOS 13.5.1 Safari