Make outgoing call with Shared Line Appearance (SLA)

I setup Asterisk SLA function based on the description from this link, and my end points are Snom phones.
smartvox.co.uk/astfaq_asteri … #AstBLFSLA:

Everything works fine except that when I try to make an outgoing call by first pressing a shared line button to seize that line and then enter the destination number, the first digit entered is omitted by Snom phone. Here is some detail, when the shared line button is pressed, an INVITE is sent and Asterisk invokes SLAStation() function. Since there is no call on the line it plays dial tone via Disa function. Now when I enter the destination number, Asterisk detects the first digit and terminates call. That’s where the problem is, Snom support claims that since the first digit entered is used to terminate the call, so it is skipped as part of the destination number.

Does Asterisk behave correctly, terminating the call when it detects digits? Does anybody have a similar setup working? If you do can you please kindly share the configuration with me?

Thanks in advance.

Yue