Stitch knit problem

after a purl stitch on a previous row why does the knit stitch show front of yarn instead of the usual position?

I’m not sure what you mean - do you have a picture? The back of a knit stitch is a purl, the back of the purl is a knit so on the next row, the sts that you worked the previous row will be ‘reversed’. It may be that you wrap your sts ‘backwards’ so the leading leg is in back of the needle instead of in front. Just knit into the first leg, the one closest to the needle and your stitches will be even and untwisted.

Take a look at the videos for knit stitch and purl stitch here (and also stockinette). They may help answer your question.