I have a 3.0 and I almost threw the darn thing out the window after taking it in every 4 to 6 months to have the tension fixed. That went on for 5 to 6 years and cost many $$$. Finally one old lad who fixes sewing machines for $35 as long as it is not an electronics problem showed me the reason I was having problems.
When you put a bobbin in the bobbin case you tread it thru the case. Before you bring up the thread there is a small square piece of metal next to where you have the thread. You must get the thread under that metal ( I use a pin to guide it). At that point the thread comes up at a 90 degree angle. Not slightly slanted.. That cured my problems with tension and, no, it is not in the manual.