Footprint grabbed by the wrong pin during a move.

Description

When I hover over a pad of a footprint and press m to move it, the footprint is often grabbed by the wrong pin. In the attached screen recording I pressed m while hovering over pin 20, but the footprint is grabbed by pin 21.

vokoscreen-2022-01-16_14-22-09.mkv

At other times, a footprint can not be grabbed by a pad at all, but it's grabbed by it's center, even when Pcb Editor / Preferences / Preferences / Pcb Editor / Editing Options / Magnetic Points / Snap to Pads is set to Always

This behavior was also observed by another user on the forum: https://forum.kicad.info/t/grab-a-component-from-the-center-of-a-pad-to-move-it/33292

Steps to reproduce

1. Hover over a pad of a footprint.
2. Depress m to move the footprint.
3. Observe that the cursor jumps and the footprint is grabbed by another pad.

After more experiments, I discovered it is related to the grid. On a coarse grid (for example 5mm) the behavior is atrocious, while at a fine grid (0.1mm) it seems to work as expected. I am guessing here, but could it be that the cursor location is first mapped to a grid point, and then that grid point is used determine the closest a snap location?

KiCad Version

Application: KiCad PCB Editor

Version: 6.0.1-79c1e3a40b~116~ubuntu20.04.1, release build

Libraries:
	wxWidgets 3.0.4

Platform: Linux 5.13.0-25-generic x86_64, 64 bit, Little endian, wxGTK, xfce, x11

	wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8) GTK+ 3.24
	Boost: 1.71.0
	OCC: 7.5.2
	Curl: 7.81.0
	ngspice: 31
	Compiler: GCC 9.3.0 with C++ ABI 1013

Build settings:
	KICAD_USE_OCC=ON
	KICAD_SPICE=ON