Unable to join the network - plusnet Sagemcom 2704n

[#1]

Could someone help me with the number of devices connected to our Sagemcom 2704n.
We have roughly 20 devices that link to the Internet on a daily basis, however we are finding that some of these devices are then logged off from automatically connecting and then unable to connect unless the Internet is switched off even though the Internet is still working on many devices throughout the house. The message given is Unable to join the network.
Does this Sagemcom 2704n only support a certain number of connected devices? If so, how can this be increased or do plusnet offer alternatives so that we are not constantly inconvenienced by having to keep switching off the Internet unit

[#2]

I don't know what the limit is for that particular router but 20 devices is a lot of connections to expect a home router to handle concurrently. Since PN gives that router away for free I wouldn't expect much of it at the best of times. With that number of devices you should probably be looking at getting a business grade router or at least the top end of the residential market.
Free routers tend to be worth everything you pay for them.

[#3]

As above.. you get what you pay for. PN give it away for nowt (although lets face it they recover that from your subscription... but even then they're sending out very cheap hardware). The point being that its cheap - and cheap usually means it'll do a basic job but nothing more (sorry!).
If you have 20 devices, maybe you should mull over the idea of making it 21 - like a more robust router? - I'm not trying to be sarcastic btw, i'm being genuine when i say it. I had no end of hassle with some low spec routers (they notably gave up after BT engineers visited) and so had to go and buy another one - being the cisco x3000 - which would want rebooting every 5-7 weeks but was rock solid other than that.
The downside was that at PC World it cost me £86 iirc.... and it didn't have a great number of features either