As we can see, the part after the #R contains the diagram, but we can see that it included two HTML tags that are URL-encoded, followed by a Base64 string. This causes an error when Draw.io attempts to call atob, as the entire string is not properly Base64-encoded, which results in a crash in the atob function and the current behavior.
Interestingly, the issue can be reproduce on the latest version of drawio.
The issue was caused by a mix of different encodings within the same text. For example, when exporting a diagram, Draw.io generates the following URL:
As we can see, the part after the #R contains the diagram, but we can see that it included two HTML tags that are URL-encoded, followed by a Base64 string. This causes an error when Draw.io attempts to call atob, as the entire string is not properly Base64-encoded, which results in a crash in the atob function and the current behavior. Interestingly, the issue can be reproduce on the latest version of drawio.