It's possible that it sounds differently when played in the unit than it does in the Incubator, but I can clearly hear the tlhay and the round 'ot on both the individual word and the full sentence. I played it for a non-Klingon speaker and he thinks it's an 'ut, even when I said tlhIp, thlop, tlhup out loud for him to pick. Which is odd, but at least confirms that it's nothing like an 'It.
I'm happy with the recording, and can't re-record now anyway, because the non-Klingon speaker is rattling about the house opining on the flavour of Ribina.
In audio reports, please specify if it's the male or female voice, and if it's the full sentence or the word tile where you have the problem. I know most of them are me right now, but eventually the guys will catch up, and you'll save us a lot of time.
I don't have a link to the sentence audio, so I can't comment on the pronunciation of this sentence now.
What I can say is that overall I find your 'otmey very similar to your 'utmey. What I think is happening is that you round the 'ot much more than most English speakers do, to the point that it pushes the 'ot farther forward in the mouth, nearly on top of the 'ut. I don't think this is a fault in your Klingon speech; I think this is just your normal accent. I hear it in your English speech, too.
My recommendation: remember to consider o to be a diphthong. It should start out not rounded, and then become rounded as you pronounce it. It's a falling diphthong, meaning the unrounded start is more prominent than the rounded ending.
He does ask for a diphthong. He says that the combination ow doesn't appear because it would be indistinguishable from o. That makes it a falling diphthong. It's not like a Spanish o, for instance, which isn't a diphthong.
The pronunciation key in The Klingon Dictionary was written and described with American accents in mind, and the sounds of Klingon should be interpreted in this way. It is not, for example, pronounced like a New Zealand o, which sounds to an American like oi or oy. A New Zealander learning Klingon shouldn't pronounce naDev yIghoS as naDIyv yUghoIyS just because they pronounce their English vowels differently than Americans.
P.S.: I'm not familiar with an American accent that rounds its o's so much they sound like u's. Some American Midwest accents strongly round their o's, but they pronounce them farther back in the mouth, making them quite different than their u's. Maybe I'm just better at distinguishing that than other people, but the strongly rounded o is definitely not a universally American feature. It's strongly associated with the northern Midwest.
No, Moe and mow sound the same. The vowel in both those words is a falling diphthong. The vowel in these is identical to Klingon o.
Listen to a native Spanish speaker (any accent) say no in Spanish. That's not a diphthong. Now listen to someone say no in Standard American English. It starts out the same as Spanish no but then turns into a glide. Now listen to someone say no in Kiwi English. It starts out the same as Spanish no but then turns into in i.
Klingon u is also a diphthong. Listen to a native Spanish speaker say tu in Spanish. That's not a diphthong. Now listen to someone say too in Standard American English. It starts out the same as Spanish tu but then turns into a glide. Klingon u is identical to the Standard American English vowel in too.
The Klingon Dictionary says ow and uw don't appear because they would be indistinguishable from o and u, respectively. That's because they're diphthongs that end in glides (the Klingon w is the glide in question).
The complete Klingon vowel inventory:
Monophthongs: a, e, I
Diphthongs: aw, ay, ew, ey, Iw, Iy, o, oy, u, uy
I think aw and uw and ew and Iw are dipthongs because they are vowels that start out as themselves and end up with the end of an o. But ow is identical to o because the w is the same as the end of an o so no difference, I don't have to change it. Do Moe and mow sound different in your accent? That would explain a lot.