I'm incredibly thankful I don't have this most of the time, but just a few days ago I got one of my occasional migraines where I get temporarily a type of aphasia that makes it so I can't remember a word other than to know the sounds coming out of my mouth are not correct, I can't parse written language, and I forget a lot of words.
It's fascinating to me because it lasts only 22 minutes, but man is it incredibly frustrating. Being intermittently aphasic is really fascinating intellectually though because I can feel/watch as the part of the brain you're describing is temporarily shut down or working improperly.
I can often say one or two words and then eight of gibberish, knowing exactly what I intended to say (in meaning, but with no valid internal monologue) but the words just coming out garbled. I can focus really hard and make a specific sound, but I can't do things like "awk" because it's too complex of a physical motion to make with my jaw and tongue. I can basically intentionally make baby sounds, occasionally a word escapes as intended, but mostly it's just bizarre obviously wrong sounds -- slightly different each time I say the word but mostly similar.
Brains and language are really weird.
With regard to your comment about thinking without monologue, I tried doing that for about a year by using some meditation techniques since it seemed like an interesting idea to avoid "mistranslation" of an idea I fully grok already into language. I'm now convinced that what happens when I talk it through to myself is that data compression is occurring that lets me store a lower fidelity, but longer lasting and more communicatable version of the concept. My memory suffered a lot that year, and many of the concepts were fully lost.