Clicking the drop-down menu under the "Vertical sync" option displays a blank drop-down menu and causes the game to freeze.
Can be recreating by going to Settings > Video > Vertical Sync and clicking the drop-down menu
MCPE-177006
Vertical Sync drop-down freezes game
Resolved
Invalid
0
There is no Vertical Sync option in the video settings, so this is an issue with the resource pack you're using.