This is a bug. You should reach out to support for information.
Here's a description I dotted down when I saw this issue once before. Not sure if it's your exact issue:
"If there is a one to many dimension match where the first dimension value contains an ampersand (&), then it, and all characters following will be suppressed.
This happens in IE ONLY, and AJAX Client ONLY. Works fine with AJAX client in Google Chrome.
QlikView Server 11 Service Release 1, Internet Explorer 8."