I've been having a similar issue for a few months now. I've got 8 cameras and have been running them with no issues for several years. I have all my cameras running through a single POE switch. Since I didn't notice any other network problems, I thought maybe my switch was bad since it is installed in a hot attic and is a couple of years old. I bought a new switch and thought I had the problem solved, but that was not it. I tried making sure all my cameras were recording directly to disk, limited the frame rates and lowered the quality of the recordings. Nothing seemed to help.
I am using an ASUS RT-AX88U router so I believed the router capability was not the problem. I updated my firmware again hoping that might be it. Then I ran a wi-fi analyzer on my network. I'm using my 5Ghz network for most of my connections so I looked at the 5Ghz band first. I noticed a lot of congestion in the channel I was using (149) and wondered if interference from other networks was causing the problem. I logged in to my router and changed the channel to one that was much less congested (165 in this case). I did that last night and I have not seen the issue since then. There is a group of townhomes next to my house so I think the odds are good that my problem stems from a large number of routers transmitting on the same channel that I was using that are well within range of my router.
If you are having this problem, you might want to look into whether this might be your issue. My cameras worked very well for a long time until someone probably moved in to a house or apartment nearby and started broadcasting with high power on the same channel I was using. That can interfere with your network in a way that looks similar to an impending or existing hardware problem.
The reason the wireless channel affected all the cameras on that switch is because the computer that hosts the
Blue Iris server is connected wirelessly to the router by wi-fi 6 connection. The adapter is an Intel AX 200 which usually maintains a connection speed of more than 700 Mbps. Even though all the cameras were connected via ethernet, they were affected by the interference with the wireless connection to the server.