[BUG] MMU2S on SKR Pro and Sensorless homing

[Minims]

Did you test the latest bugfix-2.0.x code?

Yes, and the problem still exists.

Bug Description

When enabling MMU2S on SERIAL 3 or 6, the sensorless homing ( X & Y) on a SKR Pro 1.1 with TMC2209 fails.
When home X run, it bumps but don't stop.
Same thing for home Y.

If I disable MMU2S in the configuration, sensorless homing works again.

This setup was working few months ago, but since the last bugfix2.0 I can't make it works.
Maybe it can be the 3rd serial implementation. Don't what to check.

This Printer is a CoreXY

Bug Timeline

New Bug, Discover in latest bugfix2.0, was working a the beginning of the year.

Expected behavior

Sensorless homing working with MMU2S enabled.

Actual behavior

Sensorless homing fails with MMU2S enabled.

Steps to Reproduce

Compile & Upload.
Reset EEPROM to default.
HOME X
Archive.zip

Version of Marlin Firmware

Latest bugfix (29/06/2021)

Printer model

BLV Cube

Electronics

BTT SKR Pro 1.1 , TMC2209

Add-ons

MMU2S

Your Slicer

Prusa Slicer

Host Software

No response

Additional information & file uploads

I have teste the same thing on a cartesian printer (Prusa MK2.5s BEAR) with a SKR 1.4 Turbo, TMX2209, Sensorless, MMU2S and it works.
It can be related to SKR Pro 1.1 and/or CoreXY setup

[JohnnyTheOne]

Same issue #22012

[ellensp]

Duplicate of #22012

[github-actions]

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