Sudden Unity Class UnitPortDefinition and Class ValuePortDefinition ERRORS

[SOLVED... sort of] I imported a terrain package (through the Unity Store) and then started having these errors (in the attached image). I have no idea how to fix this... It opens on every project now and won't let me proceed. I uninstalled Unity. Uninstalled again and cleaned the registry, and it persists! Please Help!!

 

Here is the contents of one of the error files ("Visual Input Definition")...

Code (CSharp):

1. using System;
2.  
3. namespace Unity.VisualScripting
4. {
5.     public sealed class ValueInputDefinition : ValuePortDefinition, IUnitInputPortDefinition
6.     {
7.         [SerializeAs(nameof(defaultValue))]
8.         private object _defaultvalue;
9.  
10.         [Inspectable]
11.         [DoNotSerialize]
12.         public override Type type
13.         {
14.             get
15.             {
16.                 return base.type;
17.             }
18.             set
19.             {
20.                 base.type = value;
21.  
22.                 if (!type.IsAssignableFrom(defaultValue))
23.                 {
24.                     if (ValueInput.SupportsDefaultValue(type))
25.                     {
26.                         _defaultvalue = type.PseudoDefault();
27.                     }
28.                     else
29.                     {
30.                         hasDefaultValue = false;
31.                         _defaultvalue = null;
32.                     }
33.                 }
34.             }
35.         }
36.  
37.         [Serialize]
38.         [Inspectable]
39.         public bool hasDefaultValue { get; set; }
40.  
41.         [DoNotSerialize]
42.         [Inspectable]
43.         public object defaultValue
44.         {
45.             get
46.             {
47.                 return _defaultvalue;
48.             }
49.             set
50.             {
51.                 if (type == null)
52.                 {
53.                     throw new InvalidOperationException("A type must be defined before setting the default value.");
54.                 }
55.  
56.                 if (!ValueInput.SupportsDefaultValue(type))
57.                 {
58.                     throw new InvalidOperationException("The selected type does not support default values.");
59.                 }
60.  
61.                 Ensure.That(nameof(value)).IsOfType(value, type);
62.  
63.                 _defaultvalue = value;
64.             }
65.         }
66.     }
67. }
68.  

 

This is the contents of the second error file (called "Visual Output Definition")...

Code (CSharp):

1. namespace Unity.VisualScripting
2. {
3.     public sealed class ValueOutputDefinition : ValuePortDefinition, IUnitOutputPortDefinition { }
4. }
5.  

 

UPDATE:

No resolution. However, I discovered that those errors in the original post only occur within one version of unity (2021.3.5.F1). I can run new projects on 2020.3.36f1 with no errors. Unfortunately my 2021 projects fail to switch to the earlier version, so fixing what is causing the errors remains unsolved.

 

I guess you can say I "solved" the problem... Complete system reimage.