no low and medium after stacking 7135s on NANJG 105C

After adding four 7135s to a new NANJG 105C 3.04A driver from the intl-outdoor shop I have no low and medium anymore. High works as intended (4.5A). On low I have no light at all but measure a few mA, on medium the LEDs die is lit and I measure a few mA more. After I removed the added 7135s the driver worked normal again.

Then I did the same experiment again using a new 105C and new 7135s but got the same result! I'm sure I didn't overheat anything and all connections are ok. What can be wrong?