You need deflectors on inside corners like that. They will divert the
gush sideways right into the gutters. Any decent gutter outfit should have
installed them.

But these are outside corners (of the main roof) not inside corners.

If you have water escaping at outside corners where the roof
doesn't funnel the water then the spillage is coming from turbulence.
When the water tries to flow around that outside corner it is impeded
just enough to overflow.

Install the elevated sidewall and it may contain the water long enough
to maintain the desired flow. It may also create a scenario where the
inside of the gutter overflows and damages the roof?