I’ve seen this before in the past, it turned out to be a network problem that is usually fixed with a better router (not the stock router the ISP’s issue) or improvements to upload bandwidth stability.
There are several other things can help, but that’s usually the main culprit. The main problem is that security cameras use upload bandwidth while a bunch of other devices are usually focussed on download, so it’s totally different. Then add to that the fact that Securities cameras need a consistent, dedicated connection and can’t benefit form “buffering” or “taking turns” like some routers try to do. There are many other things that could be said or checked. I listed some other common things related to connectivity here:
But in the above description, the main culprit is most likely the router and/or dedicated consistent upload bandwidth.