There is a recently-coined technical usage (in mathematics) of the word "anima", borrowed from Latin to English. The funny thing about this coinage is that the coin-ers of the term insist on using "anima" as both a singular and plural form of the word. They explain that the plural "should" be "animae", but that just sounds bad to them, so they use "anima" instead.
This clashes with my own sensibilities -- it seems to me that clearly the (singular, plural) forms of the word should either be (anima, animae) or else (animum, anima), or perhaps (animus, animi) if we follow the Latin, or else they should be (anima, animas) if we just anglicize everything.
But of course, it's not up to me. Even if I typically use "animae" as the plural in my own speech, I'd like to have a way to "justify" the usage of the word-coiners here, if only so that I can more comfortably slip into "their" usage when speaking to them. So this leads to my
Question: How can I "justify" this funny borrowing to myself? For example, are there other comparable examples of words borrowed from Latin into English (or between other languages) with confused declensions? Is this even a general phenomenon?