While it is true that we can't really tell what is going on without seeing footage I have a few ideas.
It is likely that your stroke varies and your shots are not super consistent. And it is likely that the balls that go into the net are balls you hit with less spin or almost dead. With this you often have the less consistent counter-hitter's ball placement less consistent.
I would not say this is anyone's fault though. If your training partner was 1-2 levels better they would adjust to the random element in your FH counterhit and the balls would keep coming back to the same place.
I have a training partner who is close to my level in match play, but who has a lot of trouble with consistency in these kinds drills that don't really have much to do with what would happen in a match.
From my perspective, I have benefited greatly from his inconsistency in the kinds of drills you are talking about. And the result has been that, when I am hitting with someone whose control is all over the place, as their spin, speed and placement keeps changing, I see it and adjust to it. And I can put the ball back to almost the same place with the same pace and spin over and over in spite of how I have to adjust to each ball. And I can also just place the ball somewhere where he can't get it if I want to. So if he goes a bit too wide, I will frequently practice going around the net and aiming for the white paint at the BH corner! [emoji2]
So, in a way, you may be doing these training partners a favor even if they don't quite realize it.
And in a match, you will never have a player trying to hit TO you and you won't be trying to hit the ball in a way to make your opponent have an easier shot.
So don't worry about this too much. As you get better, that control may come. But it also may not. I know guys who are decently high level who can't do that kind of drill at all and wouldn't do it even if they could.
I like doing them for two reasons:
1) They are meditative and relaxing. I have gone over 20 min on one ball with both BH and FH. But it really does not translate to game skills.
2) I like controlled placement. So for me it is also about being able to place the All exactly where I want while grooving the stroke.
But drills that have a random element in them are actually better for devolving skillz that translate into match play:
Watch this video. It is worth it:
Sent from The Subterranean Workshop by Telepathy