BT Smart Hub 2 users are complaining of connection issues between their wifi-enabled devices.
The telecom giant's router operates using two different wireless frequencies: 2.4Ghz and 5Ghz.
Users are complaining that any devices not linked to the same frequency, such as a phone and a speaker, are refusing to communicate with each other.
BT is offering firmware updates to those affected.
Numerous complaints have appeared on the company's community forums over the last few months.
One man said he could only connect his iPhone 11 to his Sonos speaker system when both were running on the slowest frequency.
"I can only connect the Sonos app from my iPhone, MacBook and iPad when connected to the 2.4Ghz band, which means turning off 5Ghz," said BT forum member sl_strachan.
A Sonos spokesman said on the audio firm's community forum that it had been in touch with BT, who were "aware" of the issue that is affecting a wide range of devices.
"BT have let us know that they are working towards pushing a fix to affected routers over the next 4-5 weeks," said the spokesman.
"This will be rolled out in waves due to the high number of BT Smart Hub 2 units in customers' homes, as well as making sure that the new firmware has no further issues and correctly resolves this problem."
Not enough for families
Users have found that a temporary fix appears to be forcing the Smart Hub 2 to operate on only one frequency.
Both offer advantages - 5Ghz is faster with less range, while 2.4Ghz is markedly slower but with more range. However, some older devices are incapable of operating on both.
Another BT customer said being restricted to 2.4Ghz would not be enough for families all using devices simultaneously.
"I've been having the same problems and have been tearing my hair out," said BT forum member Rawberry.
"Turning off 5GHz is a short-term workaround until the kids start streaming lots of video content, at which point the whole house slows down."
A spokesman for BT told the BBC only a "very small" number of users have been affected.
"We're aware that a very small number of customers are experiencing an issue with their Smart Hub 2 connecting with multiple streaming devices on their wi-fi network. Any customer who experiences this issue can get in touch with us and we will update their device remotely."
BT added that an update for all users would be available by the end of May.
The company did not reveal why the problem was occurring.
"We're sorry for any inconvenience caused," added the spokesman.