R3 MONOBATH DEVELOPER is a 6-minute stand developer designed to be warmed in an external water jacket to 80 degrees F (higher temperatures achieve the effect of a Push). UPDATE: Agitation may be helpful in the first minute with 35mm and rollfilm.
Trouble with streaking is less common with sheet films, where stand development (no agitation) produces a sharpness not seen with other methods.
Particularly with 35mm and rollfilms, streaks can occur from rapid cooling or temperature differentials caused by pouring the solution slowly into a cold tank. Development is rapid and the turbulence of the pour into the tank can also impact the lower portion of the film. Agitation here may help.
Also, if you are willing to experiment, try inserting a loaded real into the warm solution (rather than slowly pouring the solution in upon the film). With R3, most of the development takes place in the first few minutes.
By establishing a repeatable process that works for you, streaking can be totally eliminated.
Consult the R3 MONOBATH DEVELOPER Resource Page for further information.