Welcome to the forum.
If your unit has a 'pull out faucet', be sure the connection between the flexible hose and the faucet end is tight. Ours was a bit loose and water would flow down the hose and into the cabinet below. It seemed like a drain leak, but it wasn't really.
With things very dry, we positioned dry paper towels under the sink to pinpoint the water source.
Sherm & Terry w/rescues Steve (std Poodle) & Eydie (min Schnauzer)
2015 Jay Flight 27RLS (Camped: 102 nights 2015, 90 nights 2016)
2006 Ford F350 6.0 PSD, Lariat, 4WD, CC, LB, SRW, auto., Camper pkg.