Footprint looses net assignment when editing

Description

The central footprint (U401) loses some of its net assignment when editing the footprint on the board.

Steps to reproduce

1. Load attached project
2. Open eeschema and pcbnew
3. In pcbnew, click on U401 and select "Open in Footprint Editor"
4. Move one of the graphical lines and save to board

At this point, the footprint on the board has lost many of its assigned nets (e.g. pins 86-91). Update the board from schematic fixes this and correctly re-assigns the nets.

SiPM_Raspberry.zip

KiCad Version

Application: KiCad

Version: (5.99.0-11638-g5bf0b99813), release build

Libraries:
	wxWidgets 3.1.5

Platform: macOS Version 10.16 (Build 20C69), 64 bit, Little endian, wxMac

	wxWidgets: 3.1.5 (wchar_t,STL containers)
	Boost: 1.76.0
	OCC: 7.5.1
	Curl: 7.54.0
	ngspice: 31
	Compiler: Clang 10.0.1 with C++ ABI 1002

Build settings:
	KICAD_USE_OCC=ON
	KICAD_SPICE=ON