Hi,
concatenated filenames for org-capture templates no longer works (since 9.0).

ECM:
(setq org-default-notes-file "absolute-path/default.org")
(defvar absolute "absolute-path/"
    "Path to Desired directory.")
(setq org-capture-templates '(
("e" "Example" entry
   (file+headline (concat absolute "example.org") "Example")
   "* Capture"
   :empty-lines 1)))

Expected result:

Add "* Capture" to absolute-path/example.org.

Result: "* Capture" is added to "absolute-path/default.org".

This provides the desired result, but unable to use variable filenames (very useful):
(setq org-default-notes-file "absolute-path/default.org")
(setq org-capture-templates '(
("e" "Example" entry
   (file+headline "absolute-path/example.org" "Example")
   "* Capture"
   :empty-lines 1)))

Thanks!