Cannot change callerid when callerid is unknown on 1.2

There seems to be a problem when changing the callerid of an incoming call on version 1.2 only when the incoming callerid is witheld. On version 1.0 it used to work perfectly. On 1.0 infact when an incoming callerid was unknown the caller id would have appeared as MAIN ->

Any ideas

I am using the following for example

exten => 23880000,6,Set(CALLERID(all)=MAIN ->${CALLERIDNUM})
exten => 23880000,7,Dial(SIP/8&SIP/10&SIP/11&SIP/15&SIP/20&SIP/21&SIP/22&SIP/23&SIP/24&SIP/25&SIP/26&SIP/27&SIP/28&SIP/29&SIP/30&SIP/31&SIP/32&SIP/33&SIP/34&SIP/35&SIP/36&SIP/37&SIP/38&SIP/39&SIP/40&SIP/41&SIP/42&SIP/43&SIP/44&SIP/45&SIP/46&SIP/47&SIP/49&SIP/51&SIP/52&SIP/55&SIP/60&SIP/66&SIP/77&SIP/80&SIP/85&SIP/91&SIP/92&SIP/93&SIP/94&SIP/95&SIP/96&SIP/97&SIP/99,15)
exten => 23880000,8,Voicemail(u8)
exten => 23880000,9,Hangup
exten => 23880000,107,Voicemail(b8)
exten => 23880000,108,Hangup

For some reason when it appears

How about this:
xten => 23880000,6,Set(CALLERID(all)=MAIN - {CALLERID(num)})