How to complete a task?

Depending on the settings you choose when creating a project you might find yourself in a situation where a task is not completing and when you attempt do check it moves to another list. 

Don't panic this is just the Pipeline Workflow feature turned ON

1

Open  “Project Settings" from Inside the project view or from projects screen.

From top toolbar From projects screen
2

Navigate to the Features tab and turn Pipeline Workflow OFF

Understanding the two modes Ora Project can work in. 

1. Pipeline Workflow ON - lists have states and task state depends on their parent list. Move them to another list and their state will change. This is the default workflow for most templates and it's very useful because it will change the state for you when you drag/move cards.

2. Pipeline Workflow OFF - Open/Closed/Review tasks in the same list. In case you want mixed lists and your project doesn't follow a pipeline workflow you can disable it and have states of each individual task. When you click on a task to complete it, it completes without being moved.

Understanding Frozen, Open, Review, Closed states and lists.