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Most common issue would be the Filler/Vent hose having a crack
Looks like this:
https://www.amazon.com/1993-1997-Ford-Ranger-Filler-Clamp/dp/B00BMEU9WW
The gas flows down the smaller hose in the center and the air comes out(vents) in the larger hose
If the larger hose is cracked at the tank then it might leak only when fuel in the tank got high enough, like when filling and gas comes back up the smaller pipe to turn off the nozzle
Use your hand to feel around on the filler tube for a crack