same here. i have five ipads, all worked without any issues with 1.12, but after updating all to 1.13, all four crash within a few minutes. Not a specific action: it looks like a timed crash. The time it takes to crash is the same each time no matter what you do. start a saved world, start a new world, going through menus, or just let it sit at the title menu... and it crashes within the same number of seconds. However, the ones with more system memory last a longer time than the older ones with less...
After another hour of playing with this, I found the issue is with the 128px option and the 64px version works. All other 128px texture packs work on three other iPads, just the 128px of the Zig Zag texture pack does not work in MCBE 1.11.1.
I forgot to mention that the problem occurs across three separate devices, and the problem persists across three separate Internet service providers (Cable, DSL, and Sprint/Cell). I have tried: force-close and restart the MinecraftBedrock app (doesn't help), reboot the devices (doesn't help), and cycle power on the Internet modems (doesn't help).