Behringer somehow manufactures exclusive patented designed adapter pins, replacement of which I couldn't find in the market. The adapter pin for the BEHRINGER PSU3-UK POWER SUPPLY is quite fragile. The Round metal ring bends with a little pressure and if bent will not then enter the mixer slot. When I tried to straighten it out, one of the three extremely fragile inner pins broke. Its thinner than a needle and just about 3 mm long.
Because of this I had to replace the whole adapter. I got a genuine spare from Bajaao and it seems to work fine.
SUGGESTION: Keep the adapter connected to the mixer permanently.