Chart color shading not correctly distributing colors

I finally got through to Microsoft support, I showed them how it should work and what happens to the chart over time after it quits working properly.  The conversation went like this:

Microsoft: We are escalating the issue and we are waiting for the level 3 engineers to reach out to us, kindly bear with us to resolve this with you. Do have a great day.

Microsoft: …after my collaboration with my team, I was informed to tell you that this is a limitation with excel on MAC, and there is nothing we can do from our own end.

me: Can you explain the limitation?

Microsoft:  Limitation means that there is nothing we can do from our end here.

Me: I didn’t ask for the definition of the word “limitation”. I do know english.  What is the imitation that I am breaking to cause this bug?  If you tell me what's happening, I can find a work-around.

Microsoft: I am sorry for the inconvenience this must have caused you, but there is nothing we can do about it from our own end.

So, back to the question: is there any place to bet Excel help with a bug?