I just received my unfinished Cabreuva (Santos Mahogany). There is some wet sap on it, and, in the unopened packages there are drops of sap that look like condensation on the plastic wrap.

Is this wood safe to install (after acclimatization)?

Should I send it back to the supplier?

I don't know, you should check all the wood with a moisture meter.
Santos Mahogany is in short supply (I think) and it could possibly be getting rushed thru production. Contact the distributer anyway just to be safe.

If it has liquid sap in it then it has not been kiln dried. That in itself is not a big deal as many good woods are air dried but with wet sap it means that the moisture content of your wood is too high. It will contract once installed and leave large gaps. Second, it is impossible to use polyurethane green wood. It will bubble up and ruin the finish causing all kinds of blemishes in the surface. You could use Tung oil on green wood as it is easier to touch up but polyurethane is going to be a disaster. The really bad part is that if it is sap moisture, it takes months to air dry. That is why they kiln dry now days. If you are positive that it is sap, send it back. If it is water and no boards have warped let it acclimate in your home and it will be fine.