Jc4199, get the manual for your P89 and read it. The manual safety model you appear to have includes a decocker function in the safety. Dropping the hammer when you engage the safety is exactly what it is supposed to do. In theory, you should not be able to get the hammer to catch in "cocked" position at all with the safety on, but many P-series (including my P94) will, just barely. The slightest push on the hammer, and sometimes just gravity will turn it loose.
The P-series have a transfer bar that must be raised up to transfer the hammer's energy to the firing pin to allow the gun to fire. The only way to raise this transfer bar high enough is to pull the trigger. Thus, this is the preferred (safe) method of lowering the hammer. If you do it by holding it with your thumb, pulling the trigger, and slowly lowering the hammer, you would have the transfer bar in the firing position. If the hammer were to slip, you would potentially have an accidental discharge.
