Another glitch in the GPO5 configuration files. You can fix this as follows:

Find wherever your GPO5 instrument files are stored. (instruments, not samples.) E.g. on a Mac, it's:

/Library/Application Support/Garritan/Garritan Personal Orchestra 5/

Go to the GUI folder. Find the file named var1_var2.xml. Duplicate it, and rename the copy as n-var1_var2.xml (e.g. with n- at the front).

Timpani 3 will now display controls in ARIA Player.

One of many small corrections that ought to be made in an update.

mira!