condensation on doors Bush range cooker

Have customer who has a Bush range cooker. Whenever oven is used (either) water starts dripping on to floor withing a few minutes of getting to temperature. Apparently from door inner glass. Oven floor inside is quite dry. Anyone had this problem ? This is a relatively new cooker and this problem has existed from new. Customer says that it’s got to the point that the oven actually trips electrics on occasions but only after oven has been on for a long time.