This lighting bug seems to happen when I walk/ride through long, straight tunnels that span many chunks. The version I put in the box is incorrect but I noticed this bug before I joined the beta program so you should be able to reproduce it in 1.14 and 1.15
Thank you for reporting this issue. We're already tracking this issue at MCPE-58182. You can leave a vote on that ticket as that helps, and be sure to search before reporting in the future too.