With some of my recently changed formulas I've run into a problem. Here's a screenshot illustrating the problem:

The red bars should not be there. If I reload the fractal, the bars are different but still red. I also get different red bars with and without anti-aliasing, and different red bars when rendering. This image is with min and max threads of 20, the max on my system. With fewer threads there are fewer bars. With min and max threads of 1, no red bars.

This particular coloring uses an iteration only if the current z and the previous z are both inside a circle. My guess is that that is the source of the problem.

I get similar problems with the last 6 of the 9 "Inside/outside?" menu choices; all 6 of these use only some iterations for coloring.

Here's the upr (reload your public formulas before opening it):

/>test {

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}