Gemcutter's prism vendor recipe

Hi, I've been experiencing a bug with that recipe while trying to sell gems with a total quality of 200%, which should result in 5 gemcutter's prisms. This isn't the first time this happens to me and I always check the amount of quality to make sure each gemcutter's prism can be obtained from each 40% of gem quality I sell.

If I put the following gems in the trade window, it results in 4 gemcutter's prisms and 3 scroll fragments :

x1 19%
x1 18%
x1 17%
x1 14%
x6 12%
x1 11%
x1 9%
x3 8%
x1 6%
x2 5%

In this case, each of the following would yield a gemcutter's prism. For testing purposes, I've given a letter for the combinations I've been using to make it easier to explain.

A=12+12+11+5
B=12+8+6+14
C=12+12+8+8
D=17+5+18
E=19+12+9

The bug seems to happen when selling either A+B+C+D+E, A+B+C+E, A+C+D+E, B+C+D+E, and B+D+E, always resulting in 3 scroll fragments and one fewer gemcutter's prism than the combined quality value of the gems being sold.

https://www.poewiki.net/wiki/Vendor_recipe_system#Quality_Items

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When done for multiple instances of the recipe at once, each individual combination must add up to 40%. For example: 6 items of 19%, 13%, 15%, 9%, 17% and 7% quality would add up to 80%, but would not actually grant 2 of the resulting quality items, only 1. This is because the 2 individual combinations do not add up to 40 each.