MCEB 2.6.x Crashing after processing .mp4

You have a bad install

ERROR> 2024-02-28T11:57:03 MCEBuddy.Engine.Core --> MCEBuddy Monitor Thread Crashed. Error: System.IO.FileNotFoundException: Could not load file or assembly 'ObjectDumping, Version=1.0.0.0, Culture=neutral, PublicKeyToken=5b84c0cf1ad6e363' or one of its dependencies. The system cannot find the file specified.
File name: 'ObjectDumping, Version=1.0.0.0, Culture=neutral, PublicKeyToken=5b84c0cf1ad6e363'
   at MCEBuddy.Engine.Core.WriteJobHistory(ConversionJob job)
   at MCEBuddy.Engine.Core.MonitorEngineThread()

WRN: Assembly binding logging is turned OFF.
To enable assembly bind failure logging, set the registry value [HKLM\Software\Microsoft\Fusion!EnableLog] (DWORD) to 1.
Note: There is some performance penalty associated with assembly bind failure logging.
To turn this feature off, remove the registry value [HKLM\Software\Microsoft\Fusion!EnableLog].

This happens if you try to upgrade from a version prior to 2.6.3 directly without first uninstalling the old version: MCEBuddy Monitor Thread Crashed after first item is processed in the queue v2.6.2 - #4 by Goose

Uninstall and reinstall MCEBuddy and it should be fine.