Why does my wooden table have streaks after refinishing it three times?
As Harper mentions old poly can be a problem, but poly that is not well mixed (stirred not shaken) can also be an issue. If you sand you may well have scratches but don’t strip again--you need more coats and a very fine sand paper or fine steel wool between coats for best results. 

I have put more than a dozen coats of poly down for a gorgeous finish. Depending on wood type and the time of year I may wait 2 weeks after staining to start putting down poly. Have I ever stopped at 1 coat? Yes but not often--my “quick” quality jobs are usually 3 coats looks very nice. And with the right conditions can be done in 1 day but usually 2. 

Just a note I like wet sandpaper at 600 grit for multiple coats and have gone up to 1200 grit in the past for an absolute perfect finish. 

What do I mean about stirred not shaken? Stirring will mix the poly without introducing air bubbles like shaking will. I do shake on occasion but have a vacuum pot to pull the air bubbles out. I can’t tell if your haze is surface or below, over working poly will cause a haze to form those pesky air bubbles. In some cases it helps to thin the poly on the first coat or two if the haze is because of grain. 1-2 maybe 3 brush strokes and move on or you will create the haze by over working the poly. 

Lastly, use a very nice brush. I have brushes that cost $15-20. After use I clean them in solvent, then seal them in a jar of fresh solvent. I like solvent-based poly because I have used it for over 40 years and this method preserves the brushes. I think I am close to 7 years on the same brushes and they are almost new looking. I hope this helps.