I have recently been doing quite a bit of work on intelligibility, and some of my data comes from a male speaker from Hong Kong talking to a female speaker from Malaysia. My research is concerned with places where they failed to understand each other, and specifically with what causes those misunderstandings.
In one place, the male speaker says that he likes the steady climate of Brunei as, in previous places he has been, it has been 'either freezing cold or flaming hot'. And, as is common for speakers from Hong Kong, he simplifies the consonant clusters at the start of freezing and flaming, omitting the [r] in the first and the [l] in the second.
What is interesting from these examples is that his listener understood him perfectly well when he said 'freezing cold' but could not understand him when he said 'flaming hot'. In fact, she transcribed it as 'fuming hot' instead of 'flaming hot'.
The explanation for this is, of course, that 'freezing cold' is a common phrase (it occurs 197 times in the COCA corpus of American English ‑ see here), but 'flaming hot' is much less common (it only occurs 2 times in the COCA data).
What this tells us is this: when you are using a common phrase, then you don't need to articulate it too carefully to be understood; but if you are sayng something less common, then you need to say it very carefully.
The other thing to note is this: loss of intelligibility does not just involve pronunciation, as we have to consider other factors as well. Both of these phrases involved the same kind of non-standard pronunciation, but one was understood while the other was not.