The ClientSimBaseInput::GetMouseButtonDown method ignored the button parameter, causing the mouse event to fire for the left, middle and right buttons at the same time when only one button is pressed.

[yuxuanchiadm]

The ClientSimBaseInput::GetMouseButtonDown method ignored the button parameter, causing the mouse event to fire for the left, middle and right buttons at the same time when only one button is pressed.

ClientSim/Source/Runtime/System/ClientSimBaseInput.cs

Lines 147 to 166 in 2fc16fd

	public override bool GetMouseButton(int button)
	{
	return _lastHandUsed == HandType.RIGHT ? _rightUseDown : _leftUseDown;
	}
	public override bool GetMouseButtonUp(int button)
	{
	return
	_lastHandUsed == HandType.RIGHT
	? (!_rightUseDown && _rightUseChangeTick == _frameTick)
	: (!_leftUseDown && _leftUseChangeTick == _frameTick);
	}
	public override bool GetMouseButtonDown(int button)
	{
	return
	_lastHandUsed == HandType.RIGHT
	? (_rightUseDown && _rightUseChangeTick == _frameTick)
	: (_leftUseDown && _leftUseChangeTick == _frameTick);
	}

To replicate the issue: Add an Event System component to any UI. Then add a 'Pointer Down' event type.