ID 544557 - Inconsistent deformations when using Slack Effector

Problem summary
Inconsistent deformations when using Slack Effector.
 
Customer reported version
Modo 16.1v6
 
Customer reported platform
Windows 10
 
Steps to reproduce
1) Download the attached file, then open it in Modo.

2) Navigate to the Animation Layout.

3) Hold left mouse button and move the frame slider from zero to 60, pausing to observe at frame 30 and 60.
 
Expected behavior
Slack Effector should deform the target mesh in a consistent way.

 
Actual behavior
Slack Effector does not deform the target mesh in a consistent way.

 
Workaround
Unknown.
 
Reproduced by Support in:
Modo 16.1v6 - Windows 11, macOS 11.7 Big Sur
Modo 15.0v1 - Windows 11, macOS 11.7 Big Sur
 
 
Earliest version tested
Modo 15.0v1 - This issue appears to be in all tested versions of the product.