I once spent two days debugging confusing behaviour in a serial command interface before discovering the line:
#define CR_LF "\n"
man, that hurts. When you found the issue were you happy or were you just depressed? I've been there and sometimes finding the root of an issue is not a eureka moment but more just a long, deflating, sigh.
I was grumpy. Sometimes people are inexperienced and don't know how to make simple clean software and so end up with subtle bugs. I can understand that and dealing with it is part of life as an engineer. This was just laziness and there's no excuse for it.
"Write software like the next person to work on it is a psychopath and they know where you live"
Did you then rename the constant to NEWLINE to help the next programmer?