Since, this has only been 30-days into the usage of the printer, it maybe better to contact for warranty repair. As any fixes on your part may void your warranty. Lexmark, may just send you a replacement prtr. if no good fix helps. It certainly sounds too serious, but appears a sensor maybe flaky or blocked. Even so, that suggests a blocked sensor or kaput one. The quicker you act on this warranty wise the better the response from vendor. Contact whoever, within 30-days the seller after that the maker.

tada -----Willy Happy