I have the exact same dryer and the lint filter light does come on when you open the door before starting the cycle and when the light is finished. The cycle does not stop because of the lint signal though.
Are you sure that your dryer wasn't actually done? Don't let the time countdown fool you. The initial time on the display is just an estimate and my dryer does never take that long. It starts showing an hour and then it finishes in 35 minutes or so. I normally use the "regular" setting and sometimes an item may come out slightly damp when the load consists of very different fabrics. The "very dry" setting always got everything dry and just takes about 5 minutes longer. It sounds as if your dryer operates correctly and the sensor stops the cycle when the select dryness level is reached. The blinking light just reminds you to clean the lint filter before and after every use.

Sorry, but I don't have an answer, but we just got a Nexxt

500 also. The Lint light always lights after the dryer cycle

is over. The filter is usually fairly clean. It's small and a pain to clean.

Does your dryer make a ticking sound as the dryer drum turns.

Ours does, so does the the 2nd unit they delivered. I read
that this is a common problem. Wife will tangle with service
Monday. We like the units, though. Good luck.

The lint light turns on when the cycle is done, purely as a reminder to clean the filter. Regardless, the dryer won't shutoff until it's done or there is an error. The machine will then spin a few times, rest a while, spin again, etc. for an hour to prevent wrinkles. You can turn off the beeping if you would like. Instructions are in the manual. Are you using time dry or sensor dry? Sensor dry works very well on my machine.