When debugging on Asterisk, you generally want at least verbosity 5. Debug 5 may also be desirable.
Unfortunately, this means you will get a very large log, because of the amount of dialplan that FreePBX executes, so you need to try and look for likely problem areas before you upload it as people here are not used to ploughing through FreePBX dialplan, which they will not fully understand.
At the moment there is no evidence that the cause is FreePBX related, so I haven’t redirected you to the FreePBX forum. However, if you can reproduce the problem on bare Asterisk, with a minimal dialplan (e.g. just Dial(), it would be much easier to debug.