Extruder run differently with same configuration

Dear All,
Recently, I am working on building a delta printer which has a nozzle associated with two extruders.
It means the machine can allow one nozzle to extrude two different filaments.
The hardware has been installed well, but there are a lot of unexpected errors during configuring the marlin for the machine.
The attachment is the configuration.
The marlin passed the compiling.
the machine does work, but not correctly.
My machine has two same models of extruders.
I configured them by same parameters.
Unfortunately, They works differently when I tested them by Repetier-host.
I sent the command to ask them to extrude 100 mm filament.
the extruder 1 is OK, but extruder 2 always extrude more filament and run faster.
They were configured by same values and parameters. I don't know why they run differently.
I tried to switch the hardware of extruders to check if the extruders are different, but the result shows that the extruders are same.
Can anyone can explain this strange event? Thank you.
The attachment is my configuration.

I would guess that the micro stepping is different on your controller. E0 set to 1/16 and E1 set to 1/8, so E1 will extrude twice as much plastic.

It says its a ramps, check the jumpers under the stepper driver module

Also what could case this is if you have mixed stepper drivers, one A4988 and one DRV8825, with all jumpers on the first is 1/16, the second is set to 1/32 micro stepping.

Dear Dust,
Thank you for your reply.
I just found that it is caused by a broken A4988.
After replaced it by a new A4988, the extruder works as my expected.
Thank you!