Tasks on issue description - last write wins

I ran into a weird behaviour: when having an issue with a lot of tasks in it, if 2 people are checking/unchecking things at the same time, one will override the other changes.

The way to reproduce this is to create an issue with a lot of tasks; one user checks one task, the other user checks a different task, the first user refreshes the page, it will find that only the second task is checked.

This leads to a weird situation where both users will be checking stuff constantly overriding one another checks tasks: last write wins.

cc @jnijhof