Looks to me like you have too much paint on the roller. If its running, and you can't fix it by rolling over it some more, there's too much paint.

Its not like you roll it and sit back and wait for it to self-level: If it starts to run there's too much paint in that spot. Next time, have a second dry roller handy. Use it to re-roll any spots that start to run.

If you can feel bumps in that runny area you should sand it back down again before you try the second coat.