Hi
The Draw.io Confluence Plugin Installed version: 8.3.3
Confluence Server version: 6.13.0
I have a confluence server hosting in Azure Linux VM and running for 2 years already. And I reboot it last week due to Azure maintenance. After reboot, I get the error message "Error saving file" when I create a new diagram by the Draw.io plugin.
The error message is as below:

And I checked the console from both Chrome & Edge, they are returning a 500 ERROR from the backend.
500 ERROR:

But, when I copy an article with a diagram from the old one (the article & diagram has been created before the last reboot). Draw.io can modify it and save it.
It looks like the server is not able to save new XML files by Draw.io but I checked all-new XML created by draw.io has been saving into confluence server under /data/atlassian/application-data/confluence/attachments/ver003/206/27/1277956/35/43/91293285
The new file has been created in the server:

So, I am not sure why confluence returns "Error saving file" on Draw.io UI. Can someone answer it for me? Thanks.