The Picking Tickets show the internal ID of the Units of Measure instead of the corresponding abbreviation.
This might be caused by the Units field on the Sublist Fields not being marked as Show on the Sales Order Form. To change this setting, follow the steps below.
Open the Sales Order
On the top right corner, hover the mouse over Customize and click Customize Form
Click the subtab Sublist Fields
Locate the field Units
Mark the checkbox Show
The Picking Ticket should display the Units of Measure correctly.