Thank you for reaching out to TubeBuddy and thank you for reporting this issue.
This is due to a YouTube bug where there is sometimes a delay within YouTube Studio when we make updates using their API in the Bulk Find/Replace/Append feature. We receive a successful response from YouTube's API and the updates reflect immediately on the YouTube video watch pages (), but can sometimes take up to several hours to reflect in the text inputs on the Video Details pages in YouTube Studio (see screenshots below). We have reported this issue to YouTube's development team. YouTube is working to resolve this issue but does not have an estimated time of when it will be resolved.