In the Reddit /r/aviation thread, there are people who spotted that specific plane at San Antonio International airport since it was apparently being serviced at a major service facility there. So yes to major service potentially at issue, and no to international work being at fault.
Have you ever heard of the phrase "a distinction without a difference"? The delta between "domestic" and "international" has basically been erased for all intents and purposes over the last 25 years. H1-B can and is used for Aviation Mechanics, not to mention that approximately 25 million of the official 60 million in the US that were not born American citizens have been granted citizenship in that period.
You seem to be trying to defend "international", but reality is "international" has become "domestic" as the USA turns into something other than the USA.
Despite the enshittification of Reddit, it is still unparalleled for situations like this. There is more friction for the Fediverse to have an equivalent community, but I hope more people realize the smoothness is not free.