I tried what you shared:
when you are developing, in developer tools go to the tab application and in clear storage and clear site data
And also this one:
The Electron stores it’s cache in these folders:
Windows:
C:\Users<user>\AppData\Roaming<yourAppName>\Cache
Linux:
/home//.config//Cache
OS X:
/Users//Library/Application Support//Cache
So deleting these folders can also help you. Of course this is one time solution 
but still got the same error. Also tried to reinstall Obsidian (with clean uninstalling), still got the same error.
Then I tried with another laptop (Obsidian was fresh installed). But got the same error. So, I think it’s nothing to do with iframe cache.
Anyway thank you for the help!
If someone want to repro the error, here are the steps:
- Embed Excalidraw iframe with this code
<iframe src="https://excalidraw.com/" style="position:absolute; top:0; left:0; width:100%; border:none; height:100%;" sandbox="allow-modals"></iframe>
- in Excalidraw, try to press trash (reset the canvas) button.
The expected result is this window will pop-up. It worked when 0.9.4.

The actual result in 0.9.6 is nothing happen, and check the console then you will find this error.
