I am not seeing your sample footage but this problem most often is associated with overhead fluorescent light that causes off colored bars to move up the screen but you could also call it a flickering. I understand you also had light coming in from the windows but MAYBE this caused a mixed lighting situation where the fluorescent lighting (if it was in the room) was still having an impact.
Does your video look something like this:
https://www.youtube.com/watch?v=4Go3ksjkoKU
If so, this issue has been discussed many times on this forum so I suggest you do a search. Otherwise, feel free to try reposting that sample footage again so we can take a look
Steve Crow
PS: Just found this tool that might offer you a quick fix if you are a Final Cut Pro X, Premier or Avid user ($149):
https://www.youtube.com/watch?v=c5PrLNeF6tY
Some contents or functionalities here are not available due to your cookie preferences!
This happens because the functionality/content marked as “Google Youtube” uses cookies that you choosed to keep disabled. In order to view this content or use this functionality, please enable cookies: click here to open your cookie preferences.