"What can the problem be?"
Just the fact that SKY's wifi is probably the worst I've ever encountered since swapping from Virgin Media a decade or more ago.
I've experienced the same as you for years now and have had all the excuses going, ranging from :
Bad equipment on their part - I've had about 6 routers sent out over the years, maybe more, I've lost count.
Bad equipment on my part : I've swapped so many components out, it's untrue. They can't tell me that every single WIFI adapter / powerline adapters I've ever bought have been faulty when the equipment works at several neighbour's houses who aren't SKY customers and yet behave in the same erratic way when a neighbour is a SKY customer.
I've actually been told by CS that I don't know what I'm doing : I'm an IT tech by trade and run my own PC / IT business, having done so since the mid/late 90s.
One telephone jockey even suggested that my router had got hot and was malfunctioning because "It's been on all day", so I swapped it to one which they'd sent me whilst they waited on the phone and .. same pathetic WIFI speeds.
One was adamant that I'd been hacked and my router had been compromised. As above, swap to a previously sent out router, same issues. He reset the network, new IP for me : lasted all of several minutes before it all started again. He sent me out yet another router and within a few days, speeds were back to being terrible / not terrible / terrible again.
I've also been told that the two PCs, 1 laptop and 2 mobile phones here are all to blame and were obviously all faulty. Yeah, right ..
I've had an engineer out so often, we're on first name terms and could probably go to each other's weddings. He gave me a WIFI Booster which boosted the speeds for a while and now it's back to anything from 0.50Mbps - 45Mbps with said booster in a position showing three green lights and about 10ft ( if that ) away in line of sight from my PC's WIFI adapter. If it starts off at 80Mbps, it'll just slowly drop and drop until it hits 1Mbps - 0.50Mbps and then I lose my internet for however long it decides to not work correctly.
If I connect same WIFI adapter to my neighbour's VirginMedia network from my premises, I get upwards of 100Mbps. So it isn't my adapter, whatever they say.
When I had my Virgin Media router ( same position in house as SKY's is now ) - I never got WIFI speeds in the order of 0.50Mbps ever, it usually topped out at max speeds and stayed like it for the duration of use.
Just for the record, I was with Virgin Media for about 20 years and I can count the loss of internet and bad WIFI problems I had with them during that time on one hand. My equipment always tested out OK and always ran at full speeds - as the same still does elsewhere when I test on a non-SKY connection.
SKY on the other hand, there's been a problem almost every day and has been like that for the past 10++ years. Nothing they do seems to fix things for more then the grace period of "If you have problems for X amount of time during Y period, we'll refund you a month's fees" or whatever that clause in the contract is. Paint me cynical but ...
My equipment is fine, yours probably is too, it's just SKY's hit and miss WIFI, it's the worst I've ever encountered in a personal capacity and when visiting clients with similar issues. Mind you, they do piggy-back off BT's Open Reach, so unlike VM, the infastructure isn't theirs.
I'd happily stay a SKY customer if they sorted things out and it stayed sorted but at present, I really can't wait until OGGI gets to my area and then it's goodbye SKY. Can't say I haven't tried or given them the opportunity to fix their mess.
