All you can do is check the obvious, both elements, stats, wiring connections for breaks, condensor & heater box for blockages, dryer timer etc, any one or a combination of those could be the cause.
That reminds me of a service call I did more than 30 years ago, working for Hotpoint. Old lady complaining of poor drying. She said, ” I put it on for 15 minutes, then another 15 and another, it still wasn’t dry” :rolls: 😆