Hi Vinita,
First I want to say thank you to you and Josh (I am not sure where I got Joe from my apologies) for taking time to help.
We are on version 20.0.37253.38055 Region CA.
Vinita, to answer your questions
1.there are no customizations on the service orders, also I have check to make sure that all other customizations are installed.
2. Yes I can confirm that qty is populated. Screen shot below.

Apologies if it is to small, I am not well versed in forums .
In my sandbox I used the designer to add the Qty to ship to the field, then manually populated it, however if there are items on the service order it resets the qty to ship on resource and cost lines.
just to be clear the repo steps for this one is
create new service order, add an item, a resource and a cost , then manually add the qty to ship to each field. (with the exception of the inventory item because the warehouse documents handle that one.

I then create the warehouse shipment documents , pick sheet, ect. and "ship" the items only. After the items are shipped we usually go back to the Service order and ship and invoice on the original document so that the items and resources are on the same invoice. However when I get back to the worksheet line, the qty to ship has been reset to zero

Thank you,
Ryan