Got an error (500) "The attachment could not be opened" when downloading attachments from Calendar

We got an error "The attachment could not be opened" (status code= 500) when downloading some events' attachments.

We developed a script to download all events' attachments through graph api.

Here's what we did:

1. Use /events/{id}?$expand=attachment(select=id) to get events' metadatas and attachments' ids
2. Use /events/{id}/attachments/{id}/values to download attachments

However, we got an internal server error(500) "The attachment could not be opened" for some attachments in step 2

It looks like these attachments were deleted but the metadata still existed

We also find that this issue occurs on EWS api.

Is there any information can help us to find the root cause