.

You may also use إيماءات as an إيماءة is not as blatant and obvious as an إشارة and these cross-cultural signals are usually misinterpretations of things that are treated differently by different cultures but do not necessarily mean to derail intentions.

I don't think this expression "cross-cultural signals" can be translated exactly or word by word. You should rather go after the meaning.

إشارات عبر الثقافات
إشارات عبر تقاطع الثقافات

The quoted sentence represents a situation where a friendship is affected by the difference of (different systems in) cultures pertaining to a multicultural society. A good example of these systems is the system of worship which is very much typical in this perspective in a society like India where there are heavenly religions like Islam, Christianity & Judaism and others like Hinduism and Bhuddism etc. and their unlimited shapes with different gods. All of these sectors have their typical ways of expression at the times of happiness and sorrow, treating the dead and the ways of funeral etc.

The negative side of multiculturalism, even in absence of any physical conflict, is the disparity of humanity which reflects in the quoted sentence. It shows that the emphasis in the translation should be on "signals (إشارات)". Therefore it willl start with "إشارات"