I too have the same problem with my Dell Venue 8 Pro. I was told to send it in for a refurbished replacement and then today I get an email saying I physically damaged it so it isn't covered under warranty.
I dispute this as I have had phones, tablets and gadgets and all I have never had a single issue. They work very straight forward. It is because Dell has put into their Dell Venue 8 Pro tablets a slightly different type of micro USB which is very easy to damage. From day 1 that USB input has been very temperamental to use properly.
There is a thread on these forums of others who all have had similar problems.