September 2020 - After installing September 2020 CU and PU custom pages and controls fail to render

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After installing September 2020 CU and PU custom pages and controls fail to render. The September 2020 update includes all supported versions of SharePoint (2010, 2013, 2016, and 2019)

Review the post and comments in the link below for additional information on the issue and resolutions. 

https://blog.stefan-gossner.com/2020/09/25/trending-issue-after-installing-september-2020-cu-and-pu-custom-pages-and-controls-fail-to-render/