Beta will not update on PC from 1.3.79.1

C:\Program Files (x86)\Mission Planner\Interfaces.dll.new Failed.
System.IO.IOException: Cannot create a file when that file already exists.

at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
at System.IO.File.InternalMove(String sourceFileName, String destFileName, Boolean checkHost)
at Updater.Program.UpdateFiles(String directory) in C:\Users\mich1\Desktop\CubePilot\MissionPlanner\Updater\Program.cs:line 142
Move: C:\Program Files (x86)\Mission Planner\Interfaces.dll.new TO C:\Program Files (x86)\Mission Planner\Interfaces.dllC:\Program Files (x86)\Mission Planner\Interfaces.dll.new Failed.
System.IO.IOException: Cannot create a file when that file already exists.

at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
at System.IO.File.InternalMove(String sourceFileName, String destFileName, Boolean checkHost)
at Updater.Program.UpdateFiles(String directory) in C:\Users\mich1\Desktop\CubePilot\MissionPlanner\Updater\Program.cs:line 142
Move: C:\Program Files (x86)\Mission Planner\Interfaces.dll.new TO C:\Program Files (x86)\Mission Planner\Interfaces.dllC:\Program Files (x86)\Mission Planner\Interfaces.dll.new Failed.
System.IO.IOException: Cannot create a file when that file already exists.

at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
at System.IO.File.InternalMove(String sourceFileName, String destFileName, Boolean checkHost)
at Updater.Program.UpdateFiles(String directory) in C:\Users\mich1\Desktop\CubePilot\MissionPlanner\Updater\Program.cs:line 142

Start in Updater/Program.cs at UpdateFiles, line 142, where the failure occurs while moving Interfaces.dll.new to Interfaces.dll. Reproduce the beta update from version 1.3.79.1 and inspect the existing destination file behavior. Done means the PC update completes without the repeated IOException.

Written by the indexing model from the issue text.