Debug level is 5.
In log i can see:

[15-Apr-2017 19:31:55.282] [DEBUG] *actions* Sending SMS to NUMBER1;NUMBER2: "MESSAGE"
[15-Apr-2017 19:31:55.282] [DEBUG] SMS sender: rcpt="NUMBER1" text="MESSAGE"
[15-Apr-2017 19:31:55.282] [DEBUG] SMS: send to {"NUMBER1"}: {"MESSAGE"}
[15-Apr-2017 19:31:57.887] [DEBUG] SMS: ReadToOK: readToMark returned -1
[15-Apr-2017 19:31:58.002] [DEBUG] SMS: ReadToOK buffer content: '  OK  '
[15-Apr-2017 19:31:58.002] [DEBUG] SMS: ATZ sent, got OK
[15-Apr-2017 19:31:58.105] [DEBUG] SMS: ReadToOK buffer content: 'ATE0   OK  '
[15-Apr-2017 19:31:58.106] [DEBUG] SMS: ATE0 sent, got OK
[15-Apr-2017 19:31:58.308] [DEBUG] SMS: ReadToOK buffer content: '  OK  '
[15-Apr-2017 19:31:58.309] [DEBUG] SMS: AT+CMGF=1 sent, got OK
[15-Apr-2017 19:32:02.845] [DEBUG] SMS: ReadToOK buffer content: '    +CMGS: 236    OK  '
[15-Apr-2017 19:32:02.845] [DEBUG] SMS: AT+CMGS + message body sent, got OK
[15-Apr-2017 19:32:02.846] [DEBUG] SMS: serial port closed

[15-Apr-2017 19:32:02.846] [DEBUG] SMS sender: rcpt="NUMBER2" text="MESSAGE"
[15-Apr-2017 19:32:02.846] [DEBUG] SMS: send to {"NUMBER2"}: {"MESSAGE"}
[15-Apr-2017 19:32:05.451] [DEBUG] SMS: ReadToOK: readToMark returned -1
[15-Apr-2017 19:32:05.567] [DEBUG] SMS: ReadToOK buffer content: '  OK  '
[15-Apr-2017 19:32:05.568] [DEBUG] SMS: ATZ sent, got OK
[15-Apr-2017 19:32:05.670] [DEBUG] SMS: ReadToOK buffer content: 'ATE0   OK  '
[15-Apr-2017 19:32:05.670] [DEBUG] SMS: ATE0 sent, got OK
[15-Apr-2017 19:32:05.874] [DEBUG] SMS: ReadToOK buffer content: '  OK  '
[15-Apr-2017 19:32:05.874] [DEBUG] SMS: AT+CMGF=1 sent, got OK
[15-Apr-2017 19:32:08.576] [DEBUG] SMS: serial port closed
[15-Apr-2017 19:32:08.576] [DEBUG] Failed to send SMS (will retry)
[15-Apr-2017 19:32:08.577] [DEBUG] SMS: send to {"NUMBER2"}: {"MESSAGE"}
[15-Apr-2017 19:32:11.179] [DEBUG] SMS: ReadToOK: readToMark returned -1
[15-Apr-2017 19:32:11.294] [DEBUG] SMS: ReadToOK buffer content: '  OK  '
[15-Apr-2017 19:32:11.294] [DEBUG] SMS: ATZ sent, got OK
[15-Apr-2017 19:32:11.397] [DEBUG] SMS: ReadToOK buffer content: 'ATE0   OK  '
[15-Apr-2017 19:32:11.397] [DEBUG] SMS: ATE0 sent, got OK
[15-Apr-2017 19:32:11.600] [DEBUG] SMS: ReadToOK buffer content: '  OK  '
[15-Apr-2017 19:32:11.600] [DEBUG] SMS: AT+CMGF=1 sent, got OK
[15-Apr-2017 19:32:14.286] [DEBUG] SMS: serial port closed
[15-Apr-2017 19:32:14.286] [DEBUG] Failed to send SMS (will retry)
[15-Apr-2017 19:32:14.287] [DEBUG] SMS: send to {"NUMBER2"}: {"MESSAGE"}
[15-Apr-2017 19:32:16.891] [DEBUG] SMS: ReadToOK: readToMark returned -1
[15-Apr-2017 19:32:17.005] [DEBUG] SMS: ReadToOK buffer content: '  OK  '
[15-Apr-2017 19:32:17.005] [DEBUG] SMS: ATZ sent, got OK
[15-Apr-2017 19:32:17.107] [DEBUG] SMS: ReadToOK buffer content: 'ATE0   OK  '
[15-Apr-2017 19:32:17.107] [DEBUG] SMS: ATE0 sent, got OK
[15-Apr-2017 19:32:17.311] [DEBUG] SMS: ReadToOK buffer content: '  OK  '
[15-Apr-2017 19:32:17.311] [DEBUG] SMS: AT+CMGF=1 sent, got OK
[15-Apr-2017 19:32:19.998] [DEBUG] SMS: serial port closed
[15-Apr-2017 19:32:19.998] [DEBUG] Failed to send SMS (will not retry)
[15-Apr-2017 19:32:19.998] [DEBUG] Failed to send SMS (complete failure)
[15-Apr-2017 19:32:19.999] [DEBUG] EVENT SYS_SMS_FAILURE [30] (ID:3292 F:0x0001 S:1 TAG:"") FROM aida: Unable to send SMS to phone "NUMBER2"

I don't know why sms to first number is sent but to second not. But sometimes even sms to first number is not sent.

Thanks for your help.