If you configure a page size parameter, values that are not positive integers (or -1) will result in a 500 Internal Server Error and a stack trace. The exceptions that trigger this (vendor/zfcampus/zf-hal/src/Collection.php line 302 and 310) indicate the problem is one of validation rather than something going wonky on the server. IMHO, this should not be a 500, but could either be a 400 or 422 or it could "fail safe" back to using the configured default and not causing an error at all.