We have one DeLaval robot. It works without internet, except our phones no longer receive the "stop alarms" (something broke, need human) if the robot is offline.
There so far haven't been serious software bugs, only minor/annoying ones. Hardware, on the other hand... Things break, and then it's number one priority to fix it, even if it's 2am Sunday morning. Our poor dealer has received a number of calls in the middle of the night and/or on a weekend.
We're fairly handy though, so a decent number of problems are things we can either fix or invent a workaround for.
Most recent example: the hydraulic pump motor bearing spun in the aluminum housing, and developed so much play that the rotor actually jammed against the stator/armature. Turns out JB Kwik (faster JB Weld, epoxy) actually works to hold a bearing in place. The rotor shaft naturally tended to stay in the center (the other bearing was fine), so the epoxy cured with the bearing in the right spot, and then we were good to go.
The replacement motor has arrived but has not yet been installed.