Oops...did not mean to 'accept solution'
The vender is describing it as a 'forms overlay' and that HP has fixed it in firmware on models P3005 and the 4250/4350. (lj4240_4250_4350_fw_08_230_1.rfu)
The vendor has no word about firmware fixes for my printer models (M4345 and older 4345). Any way to encourage the same fix on other models?