Update download stalling at 75% each time

I have a Sonos beam, about 5 years old and I just changed ISP so I need to update the WiFi details for Alexa to work - however working through this process on the Sonos app it keeps failing for an unknown reason - I try a factory reset (as advised by help files) and am told I need to download an update - however the update keeps stalling.....25% downloads in about 30 seconds but then it slows down to the point where it no longer seems to be downloading - last night I re- started the process about 9pm and then left it overnight and I came down in the morning only to see it still stuck where it was when I went to bed - about 75% - surely something is wrong here? I have 500mb fibre broadband which seems to be working well, and nothing else was streaming or downloading last night - please help as I am stuck and don't know how to get past this?