When UB offer a 2 year rate, it's never exactly 2 years - it's until a specific date.
Every 6 months, they do a fixed rate hedge, so in September they did a hedge until March 2021 (2.5 years). Anyone who fixes between Sept and March will be fixed UNTIL March 2021, so you could have either 2 or 2.5 years, depending on when exactly you fix.
What happened was their template document was updated with the wrong year for a period, so a number of customers received an extra year.