I'm using a NF4V on Slingshot UFB, I was originally supplied with the horrible TP150 and upgraded at my own expense and had assistance from SS in setting up the NF4V.

One of the problems I had with the TP150 was VOIP randomly failing, in that both inbound and outbound calls are met with the "engaged" tone.  I thought this had been fixed on changing router, but over the last few weeks it seems to have come back.  All will work fine for a couple of days, then on trying to make a phone call, engaged tone.  Resetting the router or going into VOIP settings and disabling then re-enabling the SIP account clears the problem, but it's quite annoying having to do this.

Anyone else seen this? Any tips on what it might be caused by?  I haven't contacted SS about it recently because I hate going through the scripts, factory resetting the router, losing all my static IPs etc etc.