Error code 1867 | Office Integrator save to S3

I'm trying to use the Zoho Office Integrator API to edit documents saved on an S3 buckets. I can open them all right, but when pressing "save" on the frontend, this is what I get from the POST call to https://writer.zoho.eu/writer/remotesave.im:

{
"statuscode": 500,
"errorCode": "1867",
"STATUS_CODE": 500,
"RESPONSE": "postexception"
}

I have not found this error code in the documentation and am at a loss. If needed, I can provide code snippets.

Thank you in advance!

Zoho Desk Resources

Desk Community Learning Series
Digest
Functions
Meetups
Kbase
Resources
Glossary
Desk Marketplace
MVP Corner
Word of the Day

Topic Participants
Elvira
Akshaya VS

Sticky Posts
Zoho Office Integrator: Moving to the all-new Zoho Sheet
We introduced the latest version of Zoho Sheet—Sheet 5—in early 2019. This new version consists of a new user interface, improved performance, and an array of useful features. As a part of this, we will upgrade our Remote API integrations to the new version's editor interface on February 29, 2020. Update: The remote API integrations upgrade to the new version's interface will be done on April 15, 2020. Here are some exciting enhancements the new version of Sheet offers for our API users: An AI-powered
Businesses prefer Zoho Office Integrator over Microsoft WOPI - Here's why
Businesses often have difficult decisions to make when building web applications that provide document management capabilities for their users. For example, what's the best solution to integrate with online office editors— Zoho Office Integrator or Microsoft