42114 Volvo Dump Truck

I just finished the 6x6 Volvo hauler, set 42114. What a blast to build! It’s my first Technic set, and I love it! After playing with it for a few minutes, I have three questions about it. Sometimes it whines after I shift from reverse to drive or vice versa. But only sometimes. I’m not sure what I’m doing to cause this. Once it starts to whine, it doesn’t stop. Anybody know what is happening and how to stop it? Another thing I can’t figure out is how to close the LEGO Technic app. I use an...