An invalid character was found in text content (4227642)

Moment 1: Toad's working fine. Many users using Toad in the same PC, each Toad with its own user files.

Moment 2: This error come up, and Toad closes itself.

Toad for Oracle has encountered a problem. We are sorry for the inconvenience. 

An invalid character was found in text content.

It's not possible to replicate this error, it just comes out of the blue

Moment 3: When one tries to start Toad again, it starts, even connects, but, after trying to use it, it closes itself again. For example:

1.      - If one connects, and try to open the Schema Browser, Toad crashes.

2.      – Even without connecting, just starting Toad, and closing the connection window, and trying to open SQL Tracker, Toad crashes.

And this goes on and on, Toad becomes unusable.

What's been tried and hasn't helped:

A)     Renaming the user files folder.

B)     Running as Administrator.

C)     Running in compatibility mode.

All three at the same time, and restarting Toad, and the issue remains.

NOTE: having 12.6, it never had an issue, but, installing 12.11 and now the issue is there, even tested 12.12 and same as 12.11.

Toad.el shows the Error:

  --***********

  Module Name: Toad.exe - (Toad® for Oracle)

  Type       : EExternalModuleException

  Message    : An invalid character was found in text content.

  --***********