Probably the biggest issue with python.
Seemingly random changes between float64 and object happen when doing unit testing(pandas).
Can't remember the exact situation because I switched to While permanently, but there was some For loop problem. If the data came in as length 1, the for loop would read the individual chars of the string. If it came in as >1 it would iterate through the list.
15 years ago when I started python, maybe it made sense. Probably ~5-6 'oof that was a bug I wasted time' in 3 years professional use. Today, I find myself forcing types to solve a bug, or at a minimum checking the types as the program progresses.