Need help fixing caller id isses obi 110

So I have successfully managed to connect obi110 to free PBX using this tutorial:
Despite that once in a while about 25% of calls the caller id instead of being the number is obitrunk1 and it has happened to my number sometimes and sometimes its normal so it has nothing to do with the phone number but it randomly displays obitrunk1 and when that happens sometimes the phone picked up will go straight to dial tone any HELP PLS?