"heavy and sour" describes perfectly the storebought stuff I had tried years ago. Yuck, is right!
It's so sad that lefse-making has become a dying art. Making lefse takes a bit of practice, but it is sure worth the effort. I have what I call a "foolproof" recipe that came with my Heritage Lefse Plate. Instead of going through the process of cooking and ricing, or mashing the potatoes, I use Idahoan instant potatoes in the recipe and it makes delicious lefse.
Maybe someday you could try making it yourself and amaze your Norwegian relatives! ;)
Maybe I'll dig out the recipes I got in my nursing school days in ND. One of them used instant mashed potatoes if I remember correctly. Of course, I don't have an electric lefse griddle or wooden turner but the old cast iron skillet might work.