Wacom Eraser not recognised properly

Summary

I have a Lenovo L390 Yoga, which has a Wacom Digitser built in. The pen has two buttons, one of which is properly recognised as the pen's button, the other one apparently as an eraser. However, pen and eraser can't be detected at the same time. If have the eraser button pressed when bringing the pen close to the screen for the first time after a reboot, the pen is recognized as an eraser with the device Id and a pen is recognized with device id (0):

xinput list:
⎜   ↳ Wacom Pen and multitouch sensor Pen Pen (0)       id=16   [slave  pointer  (2)]
⎜   ↳ Wacom Pen and multitouch sensor Pen Eraser (0x9e54058a)   id=17   [slave  pointer  (2)]
libinput debug-events:
-event5   DEVICE_ADDED     Wacom Pen and multitouch sensor Pen seat0 default group6  cap:T  size 294x165mm calib

When I bring the pen close to the display without pressing the eraser button after a reboot, only the pen is recognized with the Id and the eraser button doesn't work:

xinput list:
⎜   ↳ Wacom Pen and multitouch sensor Pen Pen (0x9e54058a)      id=16   [slave  pointer  (2)]
libinput debug-events:
-event5   DEVICE_ADDED     Wacom Pen and multitouch sensor Pen seat0 default group6  cap:T  size 294x165mm calib

Steps to reproduce

As described in the summary

libinput version you encountered the bug on

libinput-1.13.4-1 on Arch with xorg-server 1.20.5-2, xorg-xinput 1.6.3-1 and xf86-input-libinput 0.28.2-1

Hardware information:

Lenovo Thinkpad L390 Yoga Bug occurs both with the integrated "Active Pen Pro" and the separate "Lenovo Active Pen 2"