Let’s face facts, any code slightly more complex than

10 PRINT "Hello World"
20 GOTO 10

is likely to have bugs sneak into it any time you change anything. Or even when you don’t.

Admittedly there are times when it appears that Gazillion have more people adding bugs than removing them, but that’s what you get with agile based coding practices. Especially when you keep your devs chained up in subterranean tunnels slightly less cosy than the average sewer system.