Correct technique
There are 3 outstanding trumps out. One held by opps, another by dummy, with
you holding the 3rd trump which is master. It would be easy to draw this last trump held by the opps.
BUT
You have a side suit of AKxx
The dummy holds Qxx.
If this suit breaks 3-3, with the opps having 3 cards each, then there of course will be no problem.
However, look at this in more detail. The odds are in favour of the suit breaking 4-2.
Therefore, BEFORE drawing the last trump, play 3 rounds of this side suit. If the suit DOES break 3-3, then of course you will draw the outstanding trump.
If the hand with the doubleton in the side suit also has the last trump, then he will trump the 3rd round of the suit. You will still have a trump left to trump the 4th round of the suit. You will be no better or worse off.
HOWEVER
The hand with the outstanding trump may also hold 4 of the side suit, so will be forced to follow suit while you trump the 4th round of the suit.
SUMMING UP
Always leave the outstanding trump at large while cashing a side suit with one potential loser. It can only gain.
Correct technique ensures you have no loser in the side suit.