When using Visual Studio, I get a "Object reference not set to instance of an object" error. How do I fix this error?

Question

I'm getting the following error when using Visual Studio.

For an unknown reason and at unpredictable times, the error starts showing up when I type into text boxes/fields in Visual Studio.

I can click items/objects, but I'm unable to use the keyboard to type into text boxes.

I primarily use Visual Studio for SQL development (SSIS, SSRS). We also use Team Foundation Server.

The only way I've found to fix the issue is to close and reopen Visual Studio. However, after a little while, the error returns. Unsure what causes the error to start happening.

See below for details:

Visual Studio Version Microsoft Visual Studio Professional 2017 Version 15.9.15 Installed Version: Professional

Error Details:

Object reference not set to an instance of an object. (Microsoft Visual Studio)

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Program Location:

   at System.Windows.Input.TextServicesContext.Keystroke(Int32 wParam, Int32 lParam, KeyOp op)
   at System.Windows.Input.TextServicesManager.TextServicesKeystroke(TextServicesContext context, KeyEventArgs keyArgs, Boolean test)
   at System.Windows.Input.TextServicesManager.PreProcessInput(Object sender, PreProcessInputEventArgs e)
   at System.Windows.Input.InputManager.ProcessStagingArea()
   at System.Windows.Input.InputManager.ProcessInput(InputEventArgs input)
   at System.Windows.Input.InputProviderSite.ReportInput(InputReport inputReport)
   at System.Windows.Interop.HwndKeyboardInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawKeyboardActions actions, Int32 scanCode, Boolean isExtendedKey, Boolean isSystemKey, Int32 virtualKey)
   at System.Windows.Interop.HwndKeyboardInputProvider.ProcessKeyAction(MSG& msg, Boolean& handled)
   at System.Windows.Interop.HwndSource.CriticalTranslateAccelerator(MSG& msg, ModifierKeys modifiers)
   at System.Windows.Interop.HwndSource.OnPreprocessMessage(Object param)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)