The new activity picker can be problematic where:

Monitor resolution is not sufficiently high to negate the need to scroll to see all listed activities
Activities/Resources exceed that which can be accessed without scrolling within the picker.

Suggestions:

Review positioning so that it is visible within 768px vertical res.
"Reflow" the Activity/Resource list into an additional column where available items exceed the depth of the picker.

There may be better options than the above.