My name is Arnau and I'm from Barcelona.
Over the last few years, I've been exposed to the British culture a lot (I have British friends, I've been living in Brighton for a while, I watch British TV shows, etc.) and I've kind of 'developed' a British accent. Obviously, I don't speak like a native speaker but many Brits have told me that my pronunciation is pretty good.
However, I've recently noticed that whenever I speak with non-native speakers of English (my classmates at uni, foreigners, my friends, etc.), they tend not to understand me if I speak with my 'default' accent which is non-rhotic. And in order to make them understand me, I need to repeat what I said in a rhotic accent.
So, for example, the other day I was answering a question that my math teacher asked (who's Spanish) and the conversation went like this:
MY TEACHER: What is wrong with these propositions?
ME: You have to change the order (/'ɔː.də'/).
ME: You need to change the order (/'ɔː.də'/).
TEACHER: You need to change what?
ME: The order (/'ɔː.də'/). (I pronounce it slowly and she doesn't answer anything. So, I repeat 'order' again with a rhotic accent.) The order (/'ɔːr.dər'/).
TEACHER: Ah! The order (/'or.der/).
Another situation. I was talking to a friend from France.
MY FRIEND: I don't think I'll ever pass the exam.
ME: Maybe you need to work (/wɜːk/) harder (/'hɑː.də/).
FRIEND: I need to what?
ME: Work (/wɜːk/) harder (/'hɑː.də/).
FRIEND: I don't understand you.
ME: You need to work (/wɝːk/) harder (/'hɑːr.dər/).
FRIEND: Ahh okay! Yeah, you're right.
You see what I mean? Why does this happen? Is it because when they teach us English, they only teach us the rhotic variety of English?
P.S.: This only happens to me when I speak to non-native speakers. If I talk to my British or American friends with my non-rhotic accent, I don't have any problem being understood.