Links in menu block url encoded

Have created a menu using the following:

node/add/maintenance-report?field_issueshop=[current-page:url:unaliased:args:value:2]

Yes, had to save the menu twice to get it to fix.

In the "List Links" screen of the menu, /admin/structure/menu/manage/menu-tasks, this decodes correctly to:

node/add/maintenance-report?field_issueshop=menu

However, when viewed in the menu on the live site page, it displays as

node/add/maintenance-report?field_issueshop=%5Bcurrent-page%3Aurl%3Aunaliased%3Aargs%3Avalue%3A2%5D

The menu is in a block in the sidebar of a Bootstrap-based theme.

What have I done wrong?