Bonjour/Hi jhallows:
I see you are a new member; welcome aboard.
FIrst bit of advice: Plant ID questions are best placed in the Plant Identification forum, where more eyes are available to identify your plant. This forum generally addresses questions about how to use the Dave's Garden site, finding your way around the PlantFiles, posting pictures, etc.
All that said: I will reiterate what I generally (always) say with an ID question. SHOW US THE WHOLE PLANT! Then, provide progressively more detailed images of all the plant's parts, like leaves, flowers, fruit, stems, buds, bark, etc. etc.
I think I know what is going on here, but I would like to see more information from you. You have two very clear pictures of flowers, which appear to be from different species - thus different plants. However, neither of those pictures clearly show the leaves of the plant associated with those flowers.
That is a key/critical element to see and understand. You are welcome to take as many pictures as you can that illustrate these kinds of points. The flower, then the leaf (leaves), then the branch, then the stem, and down to the ground for EACH flower you've shown.
The cluster of stems you've shown in the third picture offers some clues, but is not definitive. It appears that there is a quite old trunk in the center, and that is surrounded by some younger vigorous stems that rise rapidly without much evident foliage. There are also some much younger and greener stems at far upper left of the image. You can show us some additional pictures from different directions, so we can see how these stems arise and their relationship to the original trunk and those vigorous stems.
It may suit you best to repost this first question with these three pictures over on the Plant Identification forum. Then, provide the additional requested images that will help everyone who wishes to participate to scrutinize what is going on.
I think there are two possible answers for your puzzling situation.
The first could be that your original Viburnum with beautiful fragrant flowers (second picture above) is/was a selection of Viburnum carlesii or a closely related hybrid. That plant COULD have been a grafted specimen (rare these days, but not unheard of), and the rootstock upon which it was grafted could be responsible for that cluster of vigorous stems around the original trunk. The "fragrance" you describe for those flowers sounds to me like it belongs to Viburnum lantana, which is a hardy vigorous and reliable landscape plant in its own right, but will never be acclaimed for sweet scent. Vigorous suckering rootstock of grafted plants is not uncommon, and occurs with quite diverse plants like roses, witch-hazels, crabapples, and many other woody plants. The vigor of the rootstock can promote more rapid growth of the grafted part - thus the value of grafting. Conversely, if the rootstock suckers, then it "robs" the grafted part of the nutrients necessary for good growth, and the rootstock suckers "consume" the grafted part and essentially starve it, if you don't prune those suckers off. If this is indeed what is going on, it will be evident by very different leaf morphology for the fragrant V. carlesii plant contrasted with the less pleasant V. lantana parts. You didn't say if the original fragrant plant is still blooming for you, or if you are only getting the smelly flowers now.
The second possibility is that there is a Viburnum seedling growing in the near vicinity of your original fragrant V. carlesii. It could also be something like V. lantana or a related species/hybrid that is now growing with intertwined branches, foliage, and flowers. As unfortunate as that might be, it is an easier situation to resolve by digging out the seedling or cutting it off to kill it.
Let's see some more information! These kinds of conundrums are good challenges for the ID crowd here, and I'm fascinated that it involves a group of plants for which I have an obvious fondness.
