Erratic left-click behavior with trackball

Question

I use a Logitech Marble Mouse trackball with Mint Xfce (a recent distro change, and I'm still identifying weaknesses). It recently started to behave erratically with left-click operations:

• Grabbing a scrollbar sometimes doesn't register the click, so the scrollbar doesn't drag. Sometimes, it starts to drag, then temporarily loses recognition of the click, then re-establishes it; so the scrollbar is left in a partially moved position, and the trackball then selects an area of the screen.
• Some windows are expanded by grabbing a shaded spot in a corner and dragging. Sometimes clicking on that doesn't register, so the window can't be adjusted.

• Selecting text is an insane process. Sometimes, I'll click on the start point, drag the selection to the endpoint with the selection highlighted, release the button, and the selection disappears. Other times, it will start highlighting the selection, then at some point that highlighting will disappear and it will start highlighting again in the middle.

  Sometimes, it will start highlighting the selection or part of it, stop highlighting while I'm still moving the cursor, and the cursor movement will then drag the highlighted text to a new location.

Timing observations

There seems to be a timing element to the behavior. If I click and immediately drag, the click doesn't register. But if I click and hold for a second before dragging, the click registers, and highlighting or dragging a component begins.

The same thing happens at the end. If I reach the end of a selection and immediately release the button, it forgets the selection. But if I hold the button for a second after the selection is complete, the selection is retained.

Speculations

• There might be a setting that defines a delay before clicks are recognized, but there is no such setting in Xfce.
• There might be a memory-related issue. For example, switching between desktops often entails a delay while the system restores the selected desktop from swap; various activities have a similar lag. So the system might be busy and not recognize the button action unless the button is held until the system is no longer preoccupied and recognizes it.
• There might be a driver issue.
• There could be a problem with the trackball switch, although the other characteristics seemed to suggest a problem at the computer end.

Long story short, I finally solved it and will post an answer in case anyone else encounters the situation.

Answer 1

The problem turned out to be the trackball. The issues were replicated with other operating systems, so it wasn't Mint, Xfce, or driver-related.

I'll need to take the trackball apart to see whether the button switch is wearing out, or crud has collected in the button assembly, interfering with its operation. However, I replaced the trackball with another and the problem disappeared.

The effect of holding the button for a second apparently had nothing to do with timing. When consciously holding the button, I probably used more pressure on it, making a more reliable switch connection.