Is there a word or term to describe mispronouncing a word due to someone else's accent?

Solution 1:

I don't believe there is a specific term that describes the act of unknowingly mispronouncing a word due to somebody's foreign accent.

There are hundreds of examples where words are mispronounced by native speakers because they are unaware of the word's pronunciation. Forte is perhaps one of the best known. It can be pronounced in three different ways: /ˈfɔː.teɪ/, /fɔːt/ and /ˈfɔːr-/. The first is so commonly heard that it has practically superseded the original French pronunciation (the third). When a mistake is heard, learnt and then repeated, ESL teachers call it a fossilized error or fossilization.

Sometimes a learner’s grammatical development appears to have stopped at a certain level and recurring errors of both grammar and pronunciation have become permanent features of a learner’s speech. This is referred to as fossilization. Fossilization refers to the persistence of errors in a learner’s speech despite progress in other areas of language development. [. . .] Since fossilized errors do not generally trigger misunderstanding and hence do not prompt a clarification request from the listener, the learner may simply never notice them or be aware that they are there.

Since mathematics is often referred to as a language, mistakes in its grammar and pronunciation can be internalised by the students, especially if it is learnt through the teacher.

Solution 2:

You could say, an inherited mispronunciation. You see it in families all the time.

Solution 3:

In OP's current example of mispronounsing, it was caused by the specifics of teacher's native language, as there is no "L" sound in Japanese, so it's usually replaced by "R".

I'd go for Hyperforeignism:

non-standard language form resulting from an unsuccessful attempt to apply the rules of a foreign language to a loan word (for example, the application of the rules of one language to a word borrowed from another) or, occasionally, a word believed to be a loan word. The result reflects "neither the... rules of English nor those of the language from which the word in question comes."

The whole case is a variation of Broken English, applied to native speakers of some East Asian languages.

Engrish

a slang term for the misuse or corruption of the English language by native speakers of some East Asian languages. The term itself relates to Japanese speakers' tendency to inadvertently substitute the English phonemes "R" and "L" for one another, because the Japanese language has one alveolar consonant in place for both.