Most of time when I say a word with r before θ or ð, my tongue slides on my palate and it goes to down mouth, behind my lower teeth. This movement produce a sound similar with tap or click, sometimes the tongue don't go until down, but yet produce this different sound. I just can produce the sound properly when I say very carefully, what I think a bad behavior, because my brain need to learn do unconscious.
It's more common when I say the r before ð.
The R and the TH are okay, because R I have on my language and the TH I have learned practicing a lot.
Saying "More than four thieves" is a pretty difficult without thinking.
This noise is common when we say very fast?
Thank you ^^