Template References to offline SharePoint On-Prem Server

Hi All,

We have encountered an issue after migrating from SP 2016 into SP Online and taking the old on-prem server offline. Some templates that we have used in the past (.dotx, etc.) have references to the old SP2016 environment embedded in them. Since we have shut down our old 2016 Server, documents created with these templates take minutes to load as it appears the template reference 404's attempting to access the old server to check if the template exists. The file is loads completely fine after the check fails, as expected, because it is now a file and not the template.

I have 2 Questions:

1. Does anyone encountered this or something similar and know of a way to resolve this issue?
2. Are there ways to tell which files have been affected by this issue? We have files both locally and in SP Online that exhibit this behavior, which could mean that there are different ways to resolve this.

Thank you,