It may have thought you were taking the off ramp (GPS wobble) and rerouted on the fly.

Google maps has burned me so often, I now have a pre trip checklist for new routes. Check traffic along the entire route, the approximate on-ramp/exit #s I’ll take, and a quick look at streets around the destination.

They’ve enshittified the service so much I am just learning “normal” navigation now??? FFS.