I bet it's your rubber brake line
my 99 2500 was doing the same thing
it turns out the rubber line under the bracket collapsed because of rust
it was slow to apply and slow to release
I also replaced both front calipers before fine the bad brake line
One thing that happened to my 99 2500 was the right front rubber brake
line collapsed under the steel bracket because of rust
making that brake slow to apply and slow to release
I even replaced the caliper thinking it was bad