I've read about routers disabling 5GHz when they detect RADAR, because 5GHz can interfere with that use, and RADAR has higher priority. Here's an article on this, official from the manufacturer and for your specific model (another point for them in my book):
https://avm.de/service/wissensdatenbank/dok/FRITZ-Box-7530-A...
I wanted to say there used to be Freetz which was neat but they ensured this wouldn't work anymore. But I learned it is continued in form of Freetz-NG!
My ISP (Freedom Internet) allows me to rent a modem for 2 EUR per month. A steal.
it kept adjusting the settings I had configured after some period of time
e.g. set up a hole for SSH. I then tested it to ensure that it worked
then a few days later, trying to use it for real... finding out the device had decided to change the DNAT target ip
I replaced it with a mikrotik box that cost 1/6th as much and has functioned perfectly ever since
- Traffic prioritization (real-time, prioritized, background), and access profiles (per-device data budget, filters, max online time).
- Per device statistics on max data rate, current throughput, Wi-Fi standard, encryption, signal properties (e.g. MU-MIMO or not), etc.
- Special LAN port for guests, without access to the rest of the network (good for that ad filled smart TV).
- Extra LED with customizable function (can light up if there's anybody in the guest network, or a device plugged in the USB, or data cap is exceeded, etc).
- Energy consumption graphs for each major component (CPU, Wi-Fi, USB devices, etc).
- More information about my DSL cable than I know what to do, including spectrum graphs, line attenuation, latency, and even approximate line length.
- Security diagnostics with provider info, firmware status, login credentials type, open ports, egress filters, Wi-Fi security, etc.
- Also has features for smarthome, telephony, NAS, and media center, but I've never tried those.
[1] https://avm.de/produkte/fritzbox/fritzbox-7530-ax/