Lambda julia with black on screen

Any idea what's causing the black to appear over the fractal image? I suppose one of the variables is out of range but I happen to like the design I'm seeing on screen and don't wish to vary it too much. Thanks!

Params:

LambdaJuliaWithBlackStripe {
fractal:
  title="Lambda Julia with black stripe" width=800 height=650 layers=1
  credits="Kathy;12/31/2019" antialiasing=yes
layer:
  caption="Layer 6" opacity=100
mapping:
  center=-20.953258/-231.4272425 magn=0.00088569052 angle=-90
  transforms=2
transform:
  filename="Standard.uxf" entry="Kaleidoscope" p_symorder=2
  p_symreflect=reflective p_symcenter=-0.081/5.376 p_centermove=no
  p_angle=0.0
transform:
  filename="Standard.uxf" entry="Inverse" p_radius=1.0 p_center=0/0
  p_usescreen=no
formula:
  maxiter=50000 filename="Standard.ufm" entry="LambdaJulia"
  p_seed=1.010309351/0.2160347628 p_power=1.05416/0.056853
  p_bailout=12174.4
inside:
  transfer=none
outside:
  density=0.829476 transfer=linear
gradient:
  comments="Simple grayscale gradient." linked=yes smooth=no
  rotation=-52 index=439 color=15331327 index=454 color=5208217
  index=455 color=6762306 index=479 color=15704219 index=502
  color=6762306 index=104 color=1252454 index=134 color=2967287
  index=157 color=1513333 index=157 color=64 index=175 color=9812735
  index=202 color=64 index=202 color=4210816 index=235 color=33023
  index=255 color=799810 index=255 color=1599104 index=289
  color=1284078 index=320 color=80 index=354 color=6711036 index=395
  color=592205 index=-5 color=3488391
opacity:
  smooth=no rotation=-52 index=439 opacity=255 index=454 opacity=255
  index=455 opacity=255 index=479 opacity=255 index=502 opacity=255
  index=104 opacity=255 index=134 opacity=255 index=157 opacity=255
  index=157 opacity=255 index=175 opacity=255 index=202 opacity=255
  index=202 opacity=255 index=235 opacity=255 index=255 opacity=255
  index=255 opacity=255 index=289 opacity=255 index=320 opacity=255
  index=354 opacity=255 index=395 opacity=255 index=-5 opacity=255
}

On the Formula tab, set Periodicity Checking to "Off".

Something so simple, and yes that's the trick. So glad it works. Thank you Otto!

On the Formula tab, set Periodicity Checking to "Off".

This is such a great tip, thank you, Otto!

I must admit I have come across this problem myself once or twice in the past and never solved it. The fix is so simple and effective!