I have worked on agile projects with multiple development teams working at the same time.

Lots of developers working fast can lead to less than beautiful code

Agile development leads to requirements coming in later which change the original design of earlier code

Code degrades a bit over time due to entropy.

Agile story points are watch closely to monitor progress of teams. One of the teams needs to spend some time to refactor or clean the code to reduce the "Debt" being paid on it by all the developers.

This will involve explaining to product owner and customer that we will deliver fewer features this sprint to focus on cleaning the code.

This conversation has not gone well and the caused the customer to question the professionalism of the development team.