in bar 7 there is a break in the slur after the tie which means there is a temporary reset to the default patch before the next slur starts. If you are using note length automation in the Expression Map, this can mean switching temporarily to a short articulation like staccatissimo. If you are not using the automation then it is likely a sustain will occur instead depending on how the default is defined and here you’d notice the problem less of course.
Because libraries often have some latency built into the legato patch, Dorico does not always pick up the new slur in time. This is very library dependent but happens frequently with ones like the BBC or CS which I use. You need to experimenting with nudging the note (or the slur if possible) to ensure the legato technique is read before the note. Specific advice on the best way to do this with EWQL you’re best getting from users of Opus like @gdball.