A slip joint uses a nut and washer to seal around a drain tube. If the trap was moved to reach a stored item or during cabinet work, the tube may sit at an angle or the washer may no longer seat evenly. The joint can drip only while water drains.
Note which joint gets wet first
Look under the sink without moving the piping again. Water can travel from the sink outlet to a lower joint, so photograph the highest wet area. If the cabinet is getting wet, stop using the sink until the source is checked.
Have the alignment checked before tightening
A plumber can check tube insertion, washer fit, and whether the pieces line up without being forced. Ask for a drain test after repair and check that stored items will no longer press against the piping.
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