All the users in pick/shipping gets locked at the same time and their sessions dont get relieved

All the users in pick/shipping gets locked at the same time and their sessions dont get relieved

The lock happens in wsh_delivery_details table.

The process being followed for picking is;

a) goto Release Sales Orders form
b) enters Pick Rule and tabs through to the order number field
c) user enters Sales Order number and tabs .. the order info is populated.
d) user uses the "Execute now" button to release the order.

please advise
thanks

Balaji