I haven’t used it in a while but a common mistake could be writing ?nocalc=true if there’s already some parameter used in the doc, e.g. there’s already a ? in the URL (e.g. after ?modal=true). Then you have to specify it as the second parameter with not a ? but &, i.e. &nocalc=true.
Running my very quick tests (as I haven’t used this in a while too) this is exactly what happened when using only the DocID + ?nocalc=true in the url… Coda recreated the complete url by itself and added at the end a #_Something. The ?nocalc=true was inserted just before the #_Something.
I can’t remember how I tested this or even if I knew about the location the ?nocalc=true should take compared to the #_Something in the url but at least, now I know !
For the completeness of the answer, Coda uses the # part for navigation within the doc. Table/View/Line ID goes there along with the row ID and IIRC the parameters for modal or column ID (big text), which go after the # and not in the regular query params piece. nocalc and viewMode go before the # as regular query params. Also /_suXXX goes onto the path as page ID but it’s going to be autoresolved if #_objectID is present (it will jump to the view/table/line and prepend the page ID)