The pattern as described on the Manual page, ^wiki/([^/]+/?[^/]*)/?$, doesn't work for certain Special page operations done on subpages as it includes an additional "/".
Instead, use ^wiki/([^/]+/?[^/]*/?[^/]*)/?$ as the pattern.
Breaking it down,
- ^ - indicates the start of the string
- wiki/ - match as is
- ( - start of the {R:1} string to capture;
- [^/]+ - one or more characters that is not a slash;
- /? - once or none of the slash (basically makes it optional);
- [^/]* zero or more characters that is not a slash;
- /? - once or none of the slash, this accounts for the slash used for Special page actions, i.e. the second slash in the following "wiki/Special:MovePage/Page/Subpage";
- [^/]* - zero or more characters that is not a slash, for the "Page" in cases like the example in the previous line;
- ) - end of the {R:1} string to capture;
- /? - once or none of the slash, this accounts for the last slash before the page OR subpage name.
So, the original allows for subpages, which adds a second slash to the string to be captured, but doesn't allow for a third slash that is present when dealing with Special page operations, e.g. Special:MovePage, where the page name (or the subpage name along with the parent page name) is used in the URL.
TL;DR: use the following pattern in URL rewrite ^wiki/([^/]+/?[^/]*/?[^/]*)/?$ instead of the ^wiki/([^/]+/?[^/]*)/?$ pattern shown on the Manual page.
References: