Cannot level up on Pokemon GO(app), but action allow on PF(powerup)

[Dragonite]

Not sure if this some trick from Niantics to catch us.

I'm at lvl 25, and I've leveled my Vaporeon to the max (on app) which shows on my PF level 26.5.
But on PF, i'm still allowed to powerup my Vaporeon to level 27.

Is this somekind of mistake.