I've run into some problems when manually reordering tasks. The order won't be saved. The Agileboard backlog doesn't correlate with the Issue list.
To easier illustrate the problem see attached images.
I tried to follow the instructions on how to "Reorder Issues Manually" over here https://www.jetbrains.com/help/img/youtrack/2017.4/issueManuallySorted.png with no luck.
This is what it looks like when jumping over to the Issue list of the backlog. A completely new order.
Going back to the Agile board, list now follows the order from the "Issues list" above: