Sony vegas video lagging?

Hey, i was doing a project for school and i have 2 videos from 2 diffrent phones. One from a 1020 lumia and one from a doogee phone. Both videos dont lag in media player. The lumia one in sony vegas wich is more HD than the doogee one does not lag in sony vegas preview& after rendering but the doogee one lags in preview and after rendering too. Any suggestions?

Read more: Sony vegas video lagging?