[BUG] Lin_Advance causes erratic extruder

[rq3]

Did you test the latest bugfix-2.1.x code?

Yes, and the problem still exists.

Bug Description

Enabling Lin_Advance causes erratic extruder operation. The extruder appears to randomly reverse direction for a random number of steps, even if there are no retractions in the g-code.

Bug Timeline

Appears in all 2.1.2.3 bugfixes.

Expected behavior

The extruder should operate smoothly.

Actual behavior

The extruder is very erratic, randomly reverses direction, and generally acts as if the stepper commands and/or stepper current were wildly incorrect.

Steps to Reproduce

1. Download and install the latest bugfix (Jun 17, 2024).
2. Attempt to print known good g-code.
3. Hear and see inappropriate extruder action.
4. Disable Lin_Advance in configuration_adv.h
5. Compile and re-load firmware
6. Observe proper extruder action.

Version of Marlin Firmware

latest bugfix June 17, 2024

Printer model

Anycubic Predator

Electronics

Trigorilla Pro (STM32F1)

LCD/Controller

stock

Other add-ons

none

Bed Leveling

None

Your Slicer

None

Host Software

None

Don't forget to include

• A ZIP file containing your Configuration.h and Configuration_adv.h.

Additional information & file uploads

Configuration.zip

[thisiskeithb]

Duplicate of #27126