Stopping asterisk, starting amportal causes all inbound routes to go directly to voicemail

Hi everyone I am using FreePBX 2.8.1.5 with Asterisk 1.8.9.2 in a very busy system and some time I have to restart asterisk since the manager stops listening on port 5038 and the only way to make it start listening again is to restart asterisk:

service asterisk stop
amportal start
asterisk -rx “logger reload”

but last couple of times I did this seems like all the inbound routes are not functioning going directly to voicemail I have done some test and find out that the extensions are registered OK, and if I delete the inbound route an created again they work again (which is a task of 3 hrs of configuration since when I erase the inbound route I lost the AAstra Mac address and have to reconfigure the extensions again)

Also what I find out is that the DEVICE variable is not set when the inbound call goes directly to voice mail, Any idea and help would be greatly appreciated, thanks in advance.