Input shaping on linear delta causes Z motor clunking at specific bed locations

[droftarts]

See https://forum.duet3d.com/topic/35862/delta-z-motor-goes-clunk-regardless-of-motor-or-driver

Z motor (on Z tower) of linear delta 'clunks' when commanded to move between specific points. Reproduced in bench setup using users config.g. Happens in standalone and SBC with RRF 3.5.1, and reportedly with 3.4.2. Disabling IS and rerunning test gcode results in no clunks.

User reports different IS types, and frequencies, still results in clunks.

Tested and reproduced by @droftarts on Duet 3 6HC with RRF 3.5.1, bench test setup. An earlier test with Duet 2 Maestro on RRF 3.5.1 did not elicit any clunks, but movement was limited as testing on real machine.