.........btw Changing POI when you change power is normal for cheap scopes. Which is why on a BDC scope they tell you to sight in, and use the highest power with a BDC reticle.
It has been my experience that the power setting of the scope has to be turned to a certain value so that the BDC marks correspond to the point of impact of the load one is shooting.
Myself, i abandoned using a BDC reticle, when i learned from actual shooting that the power of the scope had to be reduced to make the various lines of the reticle fit the actual point of impact. It irritated me to turn the power of the scope down, when shooting long range. What good is a variable power scope, if one can't use the highest power to shoot the longest ranges, was how it looked to me. So.. the scope i owned with the BDC reticle, was sent back to the manufacturer for them to change the reticle to a standard duplex cross hair, and change the elevation dial to utilize a CDS dial engraved for the particular load i was hunting with at the time.