I would have to agree with both
j0hn and
kitz. The former having said you are likely out of reach is, in my opinion, almost certainly correct since your line length is probably exceeding 350-400 meters (at which point G.fast is simply unable to offer any benefits and upstream as
j0hn said would be worse).
Its quite variable though and my daughter isn't too impressed at the line can often drop out. Zen are supposed to be sending them a new router but because they can't seem to decide if its full loss of sync or loss of PPP. Lack of stats from the modem doesn't help, but there are some line stats in the relevant thread which I asked them to get from the Openreach Engineer for me.
I don't have G.fast but from the limited feedback/stats I have seen it could be said that drops seem to be a lot more common with G.fast than with VDSL (somewhat expected utilising a much larger frequency band with paper thin noise margins). Regardless of whether it resyncs in seconds, it is probably frustrating given that VDSL, for most people, can stay synced for days, weeks or, like the case here, even months.
Hopefully G.fast won't turn into G.farce, or perhaps it already was from the start.