Lighting Glitch - Light Where No Light Should Be

I built the farm and it worked flawlessly for a few hours but suddenly light filled both spawn platforms out of nowhere and broke the farm. I tore the whole thing down and rebuilt it and it worked for a few more hours before the same issue happened again. I noticed that when I broke and replaced certain blocks it would act as if I removed light sources, but all the blocks are solid blocks (dark oak wood to be specific). I have attached a screenshot of what the farm looks like on the inside. There are absolutely no real light sources in any areas of the farm.

Thank you!