System Information
Operating system: Win10
Graphics card: nVidia Quadro 600

Blender Version
Broken: 2.80 (sub 41), branch: master, commit date: 2019-01-22 16:54, hash: 25889423d324
Worked: unsure

Short description of error
It seems that if an addon makes a customization to a modal keymap, this customization only works until you restart blender. After restart, the keymap is not restored properly (left blank) and the only way to fix is to disable/re-enable the addon again.

Exact steps for others to reproduce the error

• Install and Enable the attached .py addon
  • It adds a modal keymap for circle select (makes it so that circle select is active only if you hold down the C key)
• Save Preferences

• Notice that things work correctly. Circle select is only active while holding down the C key

• Restart blender
• Notice the keymap no longer works. Check the keymap in user preferences and notice that the new entry is actually blanked out