I think the ftMatchOptions part of XQuery Full Text grammar (XQFT) is non-LL:

typeswitch (x)
case xs:integer return bla ftcontains 'hello'
case insensitive case insensitive (...) return something
default ...

This is not entirely ambiguous, but potentially requires infinite lookahead to decide whether to parse.

Another infinite lookahead required issue is the replace expression in combination with XQFT:

replace value of bla ftcontains 'x' with stemming with stemming with stemming ...