Qt6 loses track of fingers

Reproduction steps:

1. Check out the https://code.qt.io/cgit/qt/qtbase.git/tree/examples/widgets/touch/fingerpaint
2. Build the sample and run it on a screen with touch.
3. Place the index finger and start drawing.
4. Place the middle finger and start drawing.
5. Lift the index finger.
6. Place the index finger again and try to draw.
7. Note that only a single dot is placed.

Sometimes Qt behaves correctly if the fingers are placed far enough apart (it's hard to see a pattern when the bug does not appear).

Expected behavior is that the finger painting should draw more than one point when the index is placed down and dragged again.

I have reproduced this issue on multiple platforms (Windows, Linux) in our in-house application, but the issue appears straight away in the sample above.

Qt5 works fine, as does QtQuick in both Qt5 and Qt6.

Might be related to QTBUG-99426?