One would expect item becoming not supported if its parameters contains error. But currently when regular expression matching fails there is no way to tell if the expression itself was invalid or the data did not match. Therefore invalid regular expression in item parameters is not handled properly.
This affects most items that accepts regular expression in their parameters (with an exception of log(rt) items). To fix it the internal regular expression API must be reworked to allow returning of 3 states - match, not match, error (one way would be moving the matching string as output parameter and returning FAIL/SUCCEED codes).