If you're using the Asterisk manager REDIRECT command, and your calls spend a lot of their time in macros, you'll probably need to change MACRO_RECURSION. I was seeing messages like this:
[Dec 9 14:23:29] ERROR[19509]: app_macro.c:193 _macro_exec: Macro(): possible infinite loop detected. Returning early.
The macro code is deciding that's it too deep, since the REDIRECT just pushes another level onto the stack.
I'm working around this by just making the MACRO_RECURSION large in my extensions.ael file:
s = {
MACRO_RECURSION=10000;
...
Which, according to "dialplan show" turns into the old style:
Set(MACRO_RECURSION=$[10000])