I believe your webhost has started "reverse proxying" some traffic, meaning that Composr will see some hits coming from the server's own IP address rather than your own.
This confuses flood detection.
This is based on seeing the server's IP in your logs making POST requests to login, and me seeing them announcing that they have installed Nginx in front of Apache (https://www.icdsoft.com/en/news/technical/server-side-caching-now-available-846). The Server-Side caching option is turned off in your settings, but they still seem to be using Nginx. I don't know exactly when, perhaps only in circumstances affecting your particular Firefox install.
Regardless, I turned off the flood control for all your usergroups.
(Click to enlarge)
#4343 - Flood control problem
This confuses flood detection.
This is based on seeing the server's IP in your logs making POST requests to login, and me seeing them announcing that they have installed Nginx in front of Apache (https://www.icdsoft.com/en/news/technical/server-side-caching-now-available-846). The Server-Side caching option is turned off in your settings, but they still seem to be using Nginx. I don't know exactly when, perhaps only in circumstances affecting your particular Firefox install.
Regardless, I turned off the flood control for all your usergroups.