I've had broken Dahua firmware before, plenty of times. Two of my older PTZs were unable to take an IP address in the 192.168.0.X range until their firmware was updated, and the same cameras couldn't reliably operate their PTZ absolute position API (an advanced feature most people would never touch) until I updated them again about a year or two later. More recently, my 4K resolution bullet had some serious video encoding quality issues for 3 out of the 4 firmware versions I tried, and on the latest firmware that provides best video quality, I can't take advantage of the full field of view (4096x2160 doesn't work, 3840x2160 does). Lastly, all 3 of my Dahua 4MP cams (older "Themis" models) got a very slight resolution and field of view upgrade via newer firmware.
The old advice still stands though; don't upgrade firmware unless it is likely to fix something that is broken, or unless it adds a new feature you want.