Why don't part marks in a GA drawing follow part start and end points?

In our company we always ask our designers to pay attention to start and end point when creating a concrete panel since that defines the front face of the panel. In our CU drawings that front face is also the plaster surface by default. We only mark this plaster surface to drawings by text so there might be elements that are symmetrical in TS model side and the only way to tell how to erect them on site is to trust that the part marks in GA drawings indicate the orientation of parts correctly. We just don't seem to get the part marks the way we need them to be even though we have very strict rules to model the start and end point correctly. Why don't part marks in a GA drawing seem to follow part start and end points?

First thing you should consider with GA drawings and part marks is not to have the part marks on parts that you haven't yet numbered in GA drawings. The orientation of part marks might change after numbering. You can't really count on them to be correct before numbering the part and this might confuse people.

It sounds like you are using "local" as your coordinate system in your CU drawing. When using "local" as the coordinate system it means that objects in CU drawing are viewed based on the local coordinate system of the main part which means it's based on the start and end point you choose for the part when you model it. When you use this method you should however take into consideration that GA drawings use slightly different logic.

Basically part marks in GA drawing also follow the local coordinate system of the main part as well. What is probably confusing in your case is that identical parts (i.e. they have same assembly position) in GA drawing have same part mark orientation even though you have given them different start and end point. The exception with these identical parts is that if they are unsymmetrical then they are viewed in GA drawings as they are in CU drawing even if that means that part mark orientation would be different for these parts in GA drawing. But for symmetrical and identical parts the part mark orientation is the same and the part mark orientation of these parts is defined by the part that has smaller id.

Part mark orientation of symmetrical parts:

Part mark orientation of asymmetrical parts:

However there is an easy solution to your problem: Top In Form Face. Define the casting direction of parts with Top In Form Face and use that in both your CU drawings and GA drawings. The part mark orientation in GA drawings automatically follows Top In Form Face if you have defined that to a part. In CU drawings you have to define the coordinate system to be "fixed". It is preferred that you define Top In Form Face like this to a part when you want to share the info of the casting direction of a part to other as well.