There is an issue where the number of fingers detected on the touch monitor is not counted correctly.

Test Environment

• Touch Monitor: Wacom Cintiq Pro 27
• OS: Ubuntu 24.04
• Qt Version: Qt 6.8.4

Steps to Reproduce

Method 1
1. Run the attached sample application start1 and switch it to full-screen mode. The window title displays the number of fingers detected, e.g., "Fingers: 0".
2. When increasing the number of fingers one by one, the counter increases accordingly.
3. When lifting fingers one by one, the counter decreases, but at some point the count becomes incorrect, and even when all fingers are lifted, the display may remain at "Fingers: 1"

4. Once the count goes out of sync, it stays incorrect even when fingers are added or removed.
(See Touch Issue.mp4. This video starts from the state where the count is already incorrect, as described in step 3.)

Method 2
1. Run the attached sample application start4 and switch it to full-screen mode.
2. Touch the screen with multiple fingers and slide them across the monitor.
3. Ideally, lines should be drawn for all fingers in contact, but one finger (likely the first one placed) does not draw any line.
(See Touch_Finger_Lost_Issue_With_Qt6.8.4.mp4.)

Additional Notes
To check whether this issue also appears outside of Qt applications, the original reporter tested with libinput’s debug tool (debug-gui) under the same environment. The problem did not occur there. (See evtest_libinput_logs.mp4)