A few things.

Make sure you have the correct dipstick so you are not overfilling.

Make sure you have flow through the trans cooler.

Something is aerating the fluid, this can be a front pump ( torque converter ) bushing that has too large clearance or something loose on the valve body allowing fluid to spray internally.

Frothy ATF on a hot exhaust manifold will catch fire. Some manufacturers went to a locking dip stick because of this.