I experienced what seems to be a bug while playing Yortzee. During the last round of play, the two dice I had locked disappeared. They were beside each other. Tapping both empty areas made the dice reappear, and the game could conclude normally.
A few more tries at the game proved that the glitch isn't exclusive to the circumstances I noted above. Locking the dice doesn't matter. The occurrences are almost arbitrary, coming up in pairs as well, on any value, and as often as every other game it seems.
My belief is that the images failing to "load" is more the symptom, and the underlying problem has something to do with click detection and/or the table row containing the dice. When you click a die to lock it, the image isn't updated; rather, text is superimposed on it. That will work regardless if the connection to the server is intact or not, while not always for dice showing up. So it is not about how quickly the game or its resources load. Point is the dice are there, but they are obscured or invisible.