I understand that with any online game their will always be chance of lag. Either this be due to Client or Server side. This bug happened on the server side. The timer was on its last few seconds, and as soon as it hit 0, It froze for a minute or two (you could argue - Oh this is due to me having bad internet or PC. However, as this rewards screen was displayed, I highly doubt it.
As you can see, no player was awarded any crystals. Hope this gets fixed ^-^
Customer support service by UserEcho