If you have glass under the standard build plate then you will certainly will have issues with bed temperature. Have you had a look at the actual temperature across the bed? It’s likely to be very cool in the corners. There was an interesting thread about changes in bed temperature changing what appeared to be a leveling issue.
It’s all a bit tricky with a bed this size. We just have to get it as flat as possible, let the auto leveling sort out the slopes and live with the temperature differentials.