RBR850 Firmware 4.6.3.16 Internet langsam

Okay. English. But i dont' speak  English well, so it is an automatic translation:

The RBR850 router and 2 satellites received update 4.6.3.16. After the subsequent restart, the Internet became extremely slow. Internet pages do not load completely, especially if they are graphics-heavy, videos always stop, downloads are no longer possible. Restart was carried out, everything was disconnected from the mains and reconnected, a hard reset was carried out via the pinhole and the system was set up again, but all without success. The router is connected to a telecom router with a LAN connection. Internet is DSL 100,000. In the Google speed test, the display goes through to 60,000, (with old firmware up to 98,000 and remained stable there) but then drops down to zero in the further course.

After a downgrade with various annoying tricks to firmware version 3.2.18.1, which was also updated to the latest version, everything was okay again. What can I do to solve the problem? I would like to attend 3.2. Stay, since it works, the auto-update would have to be blocked so that I don't have to set everything up again every day .... Does anyone have a solution?