Before 2.4, multi line action messages were sent to modem separated by LF (\n).

In 2.4 they are sent with CR LF (\r\n) line breaks. This breaks SMS sending, at least for Teltonika GSM modem. If it gets multiline alert message, separated by CR LF, it issues another > prompt instead of saying {{+CMGS: }}.

Surprisingly GSM standard says that carrige return should be used within SMS message (http://www.etsi.org/deliver/etsi_gts/07/0705/05.03.00_60/gsmts_0705v050300p.pdf p. 56)