In the early days, we bailed out to manual resolution. In the later days, we had enough disparate data sources that we built oracles to choose which of the conflicting data was most likely to be correct.
For example, we integrated with a data source that used OCR to scan container numbers as they passed through various way points while they were on trains. The tech wasn't perfect. We frequently got reports from the rail data source that a train was, for example, passing through the middle of the country when we knew with 100% certainty that it was currently in the middle of the pacific ocean on a boat. That spurious data could be safely thrown out on logical grounds. Other cases were not as straightforward!