The Ebola vaccine in question has been tested in humans since 2015. How long-term are you looking for?
more than 5 years? Cancer risk, etc. is probably something decadal in scope.
Biology doesn't work like that. Certainly not for replication-deficient adenoviruses used by AZ, Gamaleya and J&J.
Plenty of replication deficient things cause cancer, for example asbestos or igf-1. I highly doubt you can rule out accidental crosstalk between elicited immune antibodies and every oncogenic human receptor.