Power up button missing

The option to power up now disappears at current max level. The options will return for pokemon that can be boosted further when you level up again.

Someone else was reporting this same observation a few days ago. One player was level 37 with a missing power-up button and their friend was 36 with a faded power-up button.

I can only assume that the button will return when you reach level 38.

The same thing happened to my friend at level 37. However, I'm level 40 and does not have the same problem. My friend wants to know whether this is a known bug for level 37 only? He hopes it gets fixed upon turning 38.