Not for sure what steps you took ; Here are some things to consider, : 1. the actual color of the paint you are using(whether it is a transparent color- (higher pigment concentration) which would require at least 2 coats (sometimes more) depending on the paint and primer used. Some deep bases will have more colorant added and less titanium dioxide being present.
2. The sheen of the paint you are using: with a higher sheen this can be more obvious
3. Size roller sleeve nap, roller cage being used, quality of roller sleeve, quality roller frame: Size the roller nap with the wall surface and use a quality roller cage and roller sleeve.
4. Applying to much pressure on the roller as you are releasing the paint and not doing a final ceiling to floor run.
5. Lower quality of paint
6. Try to maintain the same spread rate
7. having the roller loaded with enough paint not trying to unload every single drop of the paint .
8. Don't apply a loaded roller of paint right up against or into the previous rolled area
9. leveling out the painted rolled section with one continuous last finish roll
10. Paint should be stirred even while you are using it. Especially with a higher pigment.
11. Torque the closed end of the roller frame in the direction you are painting. Less pressure will be on the open end.
12. Use one of the telescopic handles for large walls and long passes
13. Three passes: Roll the paint on, distribute it, and finish with a last roll ceiling to floor. Different pressures for each pass.
14.Try to not have any build up of paint on the end of the roller.
Most of the time beagleowner if you let your first coat dry with the sufficient amt. of time according to the directions , by applying the second coat it will even itself out . Don't really know any of your particulars and what kind of method, rollers, how much paint you were using, etc.
If you don't have any build up of paint (heavy build up of the streakiness and something that would not need the necessity of having to sand down build up ridges), try applying your second coat , but first try to re-examine what you did in the first coat you applied. Hopefully with the second coat this will even out your finish.
or as mentioned above (Surfactant leaching)
and, I love beagles