Another angle would be that a treaty text is in just one language, but held ambiguous, on purpose, and the explanation of content presented to one party made unambiguous, and misleading on purpose, only for the deceiving party later to enforce pacta sunt servanda on one interpretation, claiming that there never was any ambiguity.
That may happen even today in many commercial situations, but a very prominent case in history was Lüderitzland:
Lüderitzland, today part of the Sperrgebiet, was far bigger than Frederiks had thought. The contract specified its width as "twintig geograph'sche mylen" (20 geographical miles), a term that the tribal chief was not familiar with; 1 German geographical mile equals 4 arcminutes (7.4 kilometers), whereas the common mile in the territory was the English mile, 1.6 kilometers. Both Lüderitz and the signing witness, Rhenish missionary Johannes Bam, knew that Chief Frederiks had no understanding of geographical miles. He was only concerned about fertile land, and the shore of the Atlantic Ocean was of no value to his tribe. When Frederiks finally became aware that the land he sold comprised almost his entire tribal area, he complained to the German Imperial Government, but Consul-General Gustav Nachtigal died on his return voyage, and the complaint was never delivered. The dodgy contract became known as the "Mile Swindle", and Adolf Lüderitz was nicknamed "Lügenfritz" (lie buddy) by his fellow countrymen. In 1887 "even the Colonial Department of the Foreign Office doubted the validity of the treaty".
And that this was completely intentional deception is evidenced by Lügenfritz writing:
In December 1882, Lüderitz sent Vogelsang to Cape Town in South Africa to explore settlement possibilities in the southwest. He was advised there by the son of the missionary Carl Hugo Hahn, who worked in South West Africa, who pointed him to the bay of Angra Pequena as a favourable landing site. Vogelsang also learned that mineral resources, e.g. copper, were to be expected in South West Africa.
After Vogelsang had the first accommodations for his expedition built in the bay of Angra Pequena in April 1883, he concluded a contract with the Nama captain Josef Frederiks II on May 1 in which the bay of Angra Pequena and the land within a radius of five geographical miles were sold to the Lüderitz company for 100 pounds in gold and 200 rifles. Vogelsang left it open whether it should be German miles to approx. 7.5 km or the shorter English miles to approx. 1.6 km. Since Lüderitz later proceeded from the German unit of measurement, the Nama saw themselves deceived, however, despite violent protests could not enforce their point of view. In August of the same year a second contract was concluded in which Lüderitz was sold the coastal strip between the Orange River and the 26th parallel and an area of 20 miles inland from each point of the coast for another 500 pounds and 60 rifles. Lüderitz wrote to his agent Vogelsang: "But let Joseph Fredericks believe for the time being that this is about 20 English miles." The questionable contractual bases of the acquisitions, commonly also called "mile fraud", brought Lüderitz the derisive name Lügenfritz early on.
Thereupon Lüderitz turned to the German Foreign Office with the request for protection for his possessions. As Imperial Chancellor Otto von Bismarck was sceptical about German colonial efforts, Lüderitz only received the vague promise that he would be granted the usual protection as any German abroad.
Evidently this was just a dirty trick, and looking closely it had neither validity – at least not in the scope intended – nor any real influence on subsequent events, other than being a legal fiction offering a convenient excuse to take and to hold by force what they wanted.