Same issue, in my case I’m moving an Actor Child Component, therefore changing its Transform Location, but the Construction Script keeps using the original Location from the Blueprint definition.
I found this other thread: Construction Script doesn't get properties that are overridden on a map instance of object which confirms the issue. The only workaround they found was to add a custom property (Blueprint Editable Variable) and work from there. Unfortunately it doesn’t replace the convenience of visually dragging an anchor…
EDIT: wait, your property is custom too so I’m not sure why it’s not working… I haven’t tried it in C++ though.