My suggestion of having the car on jackstands while a helper applies the brakes can help take the guesswork out of "Which wheel has the problem????" By trying to turn each wheel with the brake fully applied you can determine which one is holding versus which one needs more adjustment. Trying to do so by applying the brakes going down the road doesn't always tell you that. Skid marks can be dependent on surface under each tire, how much dirt under each tire, etc. Having the car jacked up eliminates those variables and can at least give you a starting point if you need further disassembly and exploration.