Error while retrieving document body of note with size 20 MB

I am developing a plugin for a CRM 2016 On Premise implementation.

The max file size setting has been set to 30,000 KB in Administration -> system settings -> Email tab.

I have a plugin which runs asynchronously on post create of notes.

The plugin checks if the note has an attachment and if the attachment is present, it gets the attachment and uploads it to sharepoint.

I have been able to load notes with attachments of up to 16 MB successfully through the plugin.

However, when I create a note with an attachment of size 20 MB, I async plugin fails with the following error:

Bad Data: Plugin data is corrupted or too large.

I read the attribute into a byte array using the ConvertToBase64 message on the documentbody attribute of the note.

Can anyone help me with the issue or suggest some approaches I can try out to troubleshoot and solve this problem?