"Missing" current on my DIY driver (LM317)

Hello folks,

yeah right. I am missing some current on my driver. . After I killed my DVD diode while engraving filled areas (30min-1h constant power) @ 300mA I ordered a new LPC 826 from Odiforce. (+ copper module)
Before I plugged it onto the driver I applied my test load.

The driver in general should output 300mA max.
The problem is, it reads only a maximum of 200mA. More like 180~200 fluctuating at fully opened potentiometer (Test-load = 4x 1N4001 + 1 ohm).
I replaced the test-load with the old DVD diode and get the same mA.
Voltage jumps between 1.4V and 2.0V.

The driver I use is this one (link to DIY driver).
It is a LM317 based driver.

I replaced C2 (47uF cap) with a 1uF cap as suggested by Cyparagon.

As I am a electronics beginner I don't know where or what part of the driver I should measure in order to see if there is a defective part.

Could it be the LM317 ?
Or the replaced C2 Cap ?

Any suggestions welcome !

i'm having the same issue with this driver (Amazon.com: AixiZ 2 pack red and IR laser diode driver 80-500mA w/TTL: Everything Else), I ran power through it without a load, so think I may have cooked it, but I don't know

for the 826 diode you'll need at least 3.7V to run that and the driver, that's probbaly why your getting low currents