It depends on your connection (ISP) the load on RLC's site which may vary from server(group) to server(group) - if you have several servers you would try to spread the load but here it seems we connect to servers by region so there may well be grouping - your PC's spec, what your PC is doing, your software because there can be memory leaks in your browser for instance, RLC's own connection to the cameras, and finally the content. So it is not a simple answer unless you do have a smoothly running decently specced machine with a decent connection you can probably put it down to problem's with RLC.
Personally I sometimes have huge problems if Nelly and Bogdan fucking - that's been the worst for me - or even on some of the zoomed in cameras at The Goddess's if she is bating or having sex. And occasionally I have them elsewhere in similar circumstances. I put this down to processing the video stream which is delivering more data when pink flesh is writhing in front of the camera. This is the same reason why we get trouble at parties. The more a picture is changing the more bandwidth an individual viewer is taking up and combined with the fact a lot may be watching then that eats up the bandwidth. However I don't know the details of the architecture so maybe each apartment has its own server or servers. And of course your system could struggle in such circumstances.
I am speculating here but financially RLC will not be wanting to pay for more servers and bandwidth then they have to and if serves for 99% of the time then the remaining 1% they will put up with the criticism for if it means they don't have to spend more. When you spec systems up as I have you try to foresee everything but equally you have a duty to your profit margin not to over spec. Most businesses do not run on large profit margins so every bit you can save counts.