I have an app that uses a dynamic dockitem with the following code:
app.DockItem.ResetIcon
app.DockItem.Graphics.DrawPicture(yellow1024,0,0,1024,1024)
app.DockItem.UpdateNow
It works as expected in 32-bit but doesn’t update in 64-bit. Are dockitems handled differently between the two versions?
I’m not seeing anything specific to 64 bit. File a Feedback report on it.
I created a sample project to submit with a feedback report but I couldn’t reproduce the problem in the sample project so I’m going to have to look through the original project further to see if there may be a coding problem somewhere, although it’s still a mystery as to why it would work in 32-bit but not 64-bit.
The joys of bug reporting…
In your project, are you using liberals for the coordinates or are you using variables? Remember, Integer changes size in 64-bit.
avoid conservatives for coordinates 
It doesn’t appear to be a coordinate problem. The app normally runs hidden and the app icon reflects the last result by changing the color of the dock icon. In 64-bit the dock icon updates if the UI is open but not when the UI is hidden whereas the dock icon updates as expected when the UI is hidden in 32-bit. It’s unfortunate that the debugger is disabled in 64-bit. This appears to be a refresh problem with the dock icon when the UI is hidden.
This mystery has been solved and it turns out to have been a problem with App Wrapper overwriting the icon information in the source file. The problem disappeared after I dragged a 1024x1024 png into the App Wrapper icon window and let it make the icon files. I didn’t see the problem in 32-bit because I was testing it from the debugger rather than a build.