Actually, I ran into the same problem.
This seems to be a problem of probability, but after I switched to gulp4.5, the situation improved a lot.
You can check your [output] file in the fold [CalcFold1], that's the output data of gulp.
If the warning comes out, it usually because the warning
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*****too many failure failed attempts to optimise*****
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also comes out.
If the output file shows
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**** Optimisation achieved ****
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everything will be fine.
I think it's because the parameter setting of gulp is not so good, if you can change some of the parameters in the fold [Specific], you can solve the problem.
Since I am a beginner fo gulp, I don't know how to fix it, if anyone knows, please tell me.
Regards
Zhang Yaotang