The redstone lamp seems like it will be lighted up before the redstone signal come. Like what in picture 00.05.20. Or maybe this is a bug of the repeater. At least I can’t differentiate them just by the game.
  I record a video about it. But from on to off will only take a maximum of 0.4 seconds. So, it might not help. Thus, I use Adobe Premiere to check it frame by frame. The setting of the video is 30fps, and those screenshots below are some important frames named “min.sec.frame” which can also be found in the bottom left corner of those pictures.
  According to my checking, if there are no bugs about the repeater and redstone wire, the lamp is 1 tick early to light up. But the quenching of the lamp is normal if I remember it right (1 tick/0.1s after the signal end).