Graph Api File Upload to Sharepoint Library Json Format Error

I'm trying to upload a simple txt document to a sharepoint library, from power apps, using this tutorial.

I think I'm doing it right, troubleshooted a lot of permissions issues trough the process, but I got stuck in this error:

Unabel to read JSON request payload.

I'm just sending a put request using this:

Office365Groups.HttpRequest(
        "https://graph.microsoft.com/v1.0/sites/{mySiteId}/drives/{myDriveId}/root:/file.txt:/content:",
        "PUT",
        ThisRecord.Value
    ) 

mySiteIdid and myDriveId, I got them both correct. ThisRecord.Value is the file content from the attachment field.

I also get the same result if I try this on the Graph Explorer.

It clearly states in the documentation, that the payload should be text/plain.

• Why would it ask for a json content-type if the documentation states
  for a text/plain payload?
• Any clues on how to move forward?

It works fine if you remove : of the url

/v1.0/sites/{mySiteId}/drives/{myDriveId}/root:/file.txt:/content:
/v1.0/sites/{mySiteId}/drives/{myDriveId}/root:/file.txt:/content

I would also set the Content-Type parameter to text/plain

Office365Groups.HttpRequest(
    "https://graph.microsoft.com/v1.0/sites/{mySiteId}/drives/{myDriveId}/root:/file.txt:/content",
    "PUT",
    ThisRecord.Value,
    "text/plain"
) 

Office 365 group - send HTTP request