If I load into a saved via a quick load or using the "Continue" node, the screen will fade out as normal, the scene will load, but then it will not fade in. The first error the console gives is

Info contained in console:
Error while parsing XML data: at GamingIsLove.Makinom.IO.XMLParser.DoParse () [0x001fd] in <717287fcefd648a999a72603eb963862>:0
UnityEngine.Debug:LogError (object)
GamingIsLove.Makinom.IO.XMLParser:DoParse ()
GamingIsLove.Makinom.IO.XMLParser:DoParse ()
GamingIsLove.Makinom.IO.XMLParser:DoParse ()
GamingIsLove.Makinom.IO.XMLParser:DoParse ()
GamingIsLove.Makinom.IO.XMLParser:DoParse ()
GamingIsLove.Makinom.IO.XMLParser:DoParse ()
GamingIsLove.Makinom.IO.XMLParser:Parse ()
GamingIsLove.Makinom.SaveGameHandler:LoadFile (int)
GamingIsLove.Makinom.SaveGameHandler:CreateFileInfo (int)
GamingIsLove.Makinom.SaveGameHandler:CreateInfos ()
GamingIsLove.Makinom.SaveGameHandler:GetFileInfo (int)
GamingIsLove.Makinom.SaveGameHandler:GetFileList (bool,bool,System.Collections.Generic.List`1,System.Collections.Generic.List`1,GamingIsLove.Makinom.UI.AddCancelButton,GamingIsLove.Makinom.UI.UICustomInputSettings,GamingIsLove.Makinom.UI.UICustomInputSettings)
GamingIsLove.Makinom.UI.SaveGameControl:ShowFiles ()
GamingIsLove.Makinom.UI.SaveGameControl:Show ()
GamingIsLove.Makinom.UI.SaveGameControl:Show (GamingIsLove.Makinom.Notify,GamingIsLove.Makinom.Notify,int)
GamingIsLove.Makinom.Schematics.Nodes.SaveGameMenuNode:Execute (GamingIsLove.Makinom.Schematics.Schematic)
GamingIsLove.Makinom.Schematics.Schematic:ExecuteNextNode ()
GamingIsLove.Makinom.Schematics.Schematic:Start ()
GamingIsLove.Makinom.Schematics.Schematic:PlaySchematic (object,GamingIsLove.Makinom.Schematics.ISchematicStarter,object,object,bool,GamingIsLove.Makinom.MachineUpdateType,int)
GamingIsLove.Makinom.GlobalMachine:Call (object,object,GamingIsLove.Makinom.Schematics.ISchematicStarter,int)
GamingIsLove.Makinom.GlobalMachine:Tick ()
GamingIsLove.Makinom.GlobalMachinesSettings:Tick ()
GamingIsLove.Makinom.Maki:FireTick ()
GamingIsLove.Makinom.MakinomHandler:Update ()
The second error the console is giving me

Info contained in console:
NullReferenceException: Object reference not set to an instance of an object
GamingIsLove.ORKFramework.Combatants.CombatantAI..ctor (GamingIsLove.ORKFramework.Combatant owner) (at <6c1ba97935f44509b5fe401b20bed162>:0)
GamingIsLove.ORKFramework.Combatant.BaseInit (GamingIsLove.ORKFramework.CombatantSetting cs, GamingIsLove.ORKFramework.Group group, System.Boolean showNotification, System.Boolean showConsole, System.Boolean loadGame) (at <6c1ba97935f44509b5fe401b20bed162>:0)
GamingIsLove.ORKFramework.Combatant..ctor (GamingIsLove.Makinom.DataObject data, System.Boolean loadPosition, GamingIsLove.ORKFramework.Group group) (at <6c1ba97935f44509b5fe401b20bed162>:0)
GamingIsLove.ORKFramework.Group.LoadMembers (GamingIsLove.Makinom.DataObject data, System.Boolean loadPositions) (at <6c1ba97935f44509b5fe401b20bed162>:0)
GamingIsLove.ORKFramework.ORKPlayerHandler.LoadGame (GamingIsLove.Makinom.DataObject data) (at <6c1ba97935f44509b5fe401b20bed162>:0)
GamingIsLove.ORKFramework.ORKSaveGameHandler.Loaded (GamingIsLove.Makinom.DataObject data) (at <6c1ba97935f44509b5fe401b20bed162>:0)
GamingIsLove.Makinom.SaveGameHandler.Loaded (GamingIsLove.Makinom.DataObject data) (at <717287fcefd648a999a72603eb963862>:0)
GamingIsLove.Makinom.Components.SceneChanger+d__26.MoveNext () (at <717287fcefd648a999a72603eb963862>:0)
UnityEngine.SetupCoroutine.InvokeMoveNext (System.Collections.IEnumerator enumerator, System.IntPtr returnValueAddress) (at <685c48cf8f0b48abb797275c046dda6a>:0)
UnityEngine.MonoBehaviour:StartCoroutine(IEnumerator)
GamingIsLove.Makinom.Components.SceneChanger:OnSceneLoaded()
GamingIsLove.Makinom.Maki:FireSceneLoaded()
GamingIsLove.Makinom.Maki:OnSceneLoaded(Scene, LoadSceneMode)
UnityEngine.SceneManagement.SceneManager:Internal_SceneLoaded(Scene, LoadSceneMode)
Not really sure what happened, It worked one moment and then later it decided it didn't want to work anymore.
Another cause could be having 2 separate Unity projects with the same game/company name (in the Unity project settings), which leads to them using the same folder for save games (e.g. when using Persistent Data Path for the save files).
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In the end, I just deleted all the files in the project from the data folder in Ork/Maki directory. It fixed it.