A_ is used in the parameter script, which is GLOB_SCALE in old form. That may cause problems: its default value is set to 100 in paramscript, so your object works fine in 1:100, but starts to behave strangely in any other scale.
The warning is not “visible”, because you use the global in a valid condition, and this specific warning only works while interpreting the script (this was necessary because master script can use restricted globals in script-type dependent conditional expressions).
Dominika Bobály
Product Manager
GRAPHISOFT SE