Thinking about it, I don’t think it should be a problem: I think adl_smsSend() does complete the SMS command(s) before it returns - so there shouldn’t (sic!) be a problem…
Does your application also receive SMS 
If so, do you also have problems with SMS reception…?
There is a longstanding suspicion that something can go wrong with SMS reception, resulting in the receive handler not being notified: Received SMS messages not reaching the SMS Handler
I’m not sure what happens to SMS sending in that case…