Windows [HELP] Multiplayer host crashes after logging invite code, map is from before latest update

[oysters]

Title has most of it. When selecting Co-op and a particular map, the host starts, the screen is black, then the log on the bottom left reports that a game has been created with the invite code. The host then crashes. This occurs consistently. This is the error log:

Message: The content file was not found.
InnerException: System.IO.FileNotFoundException: Could not find file 'C:\Program Files (x86)\Steam\steamapps\common\Stardew Valley\Content\Characters\MarlonFay.xnb'.
File name: 'C:\Program Files (x86)\Steam\steamapps\common\Stardew Valley\Content\Characters\MarlonFay.xnb'
   at System.IO.FileStream.ValidateFileHandle(SafeFileHandle fileHandle)
   at System.IO.FileStream.CreateFileOpenHandle(FileMode mode, FileShare share, FileOptions options)
   at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options)
   at Microsoft.Xna.Framework.TitleContainer.PlatformOpenStream(String safeName) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\MonoGame.Desktop\MonoGame.Framework\Platform\TitleContainer.Desktop.cs:line 29
   at Microsoft.Xna.Framework.TitleContainer.OpenStream(String name) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\MonoGame.Desktop\MonoGame.Framework\TitleContainer.cs:line 37
   at Microsoft.Xna.Framework.Content.ContentManager.OpenStream(String assetName) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\MonoGame.Desktop\MonoGame.Framework\Content\ContentManager.cs:line 276
Stack Trace:    at StardewValley.SaveGame.getLoadEnumerator(String file)+MoveNext() in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\Farmer\Farmer\SaveGame.cs:line 1828
   at StardewValley.Game1.UpdateTitleScreen(GameTime time) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\Farmer\Farmer\Game1.cs:line 6307
   at StardewValley.Game1._update(GameTime gameTime) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\Farmer\Farmer\Game1.cs:line 4906
   at StardewValley.Game1.Update(GameTime gameTime) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\Farmer\Farmer\Game1.cs:line 3974
   at StardewValley.GameRunner.Update(GameTime gameTime) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\Farmer\Farmer\LocalMultiplayer.cs:line 1067
   at Microsoft.Xna.Framework.Game.DoUpdate(GameTime gameTime) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\MonoGame.Desktop\MonoGame.Framework\Game.cs:line 814
   at Microsoft.Xna.Framework.Game.Tick() in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\MonoGame.Desktop\MonoGame.Framework\Game.cs:line 567
   at Microsoft.Xna.Framework.SdlGamePlatform.RunLoop() in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\MonoGame.Desktop\MonoGame.Framework\Platform\SDL\SDLGamePlatform.cs:line 91
   at Microsoft.Xna.Framework.Game.Run(GameRunBehavior runBehavior) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\MonoGame.Desktop\MonoGame.Framework\Game.cs:line 481
   at StardewValley.Program.Main(String[] args) in C:\GitlabRunner\builds\Gq5qA5P4\0\ConcernedApe\stardewvalley\Farmer\Farmer\Program.cs:line 175

Game Version: 1.5.6 Hotfix #3
SDK Helper: SteamHelper
Game Language: en
GPU: GeForce GTX 1060 3GB/PCIe/SSE2
OS: Win32NT Microsoft Windows NT 10.0.19043.0
In-game Date: summer 24 Y5 Time of Day: 600
Game Location: FarmHouse

Is anyone aware of a specific fix or a good next place to look?
Thanks!