Undermount sinks generally use a combination of adhesive and sink clips to hold them in place. Some of our Allies have had their sink fall and in most (but not all) cases, they travelled with dishes, coffee makers etc, in the sink. The moment weight of material stored in the sink when the coach is bouncing down the road can be problematic.
That all said, I am not suggesting this is the cause for your sink failure. As
@Oregon_Camper has suggested, please provide some pictures showing the underside of the sink where the sink edge meets the counter top bottom.
Here's a link to what various sink clip styles. If you were to DIY repair using new sink clips, be very careful as to the length of screw you would use to go into the counter top wood substrate. I think it's only maybe 3/8" thick.
Also, feel free to email your pictures, a description of what is happening, your name, phone and last 6 of your VIN to our service team at
service@alliancerv.com.