So this is NEW… 
I posted the other day about an issue with Revit>DataSmith>TM not being able to re-import the DS file. There was a recent Hotfix which resolved that issue. I had continued to work in the TM file, placing entourage, trees, etc. prior to the fix and it’s update.
One tool I used was the Spacing Tool to place cars parked along the street at the curb. Got it to work nicely. I have added some tree models I purchased from the Marketplace. They look great! However, once the Hotfix was applied, the cars… now identify as Birds… as they are up in the trees. Nicely placed & oriented well, I might add, amongst the branches. It is unclear if their horns now sound like tweets. 
The branches do extend over the cars below, so somehow the tool is ‘seeing’ the geometry up there and then displacing/placing the cars. Why would this do that? The ‘control line’ is placed on the road geometry (can be seen in the pic). While working in the file prior to the Hotfix (and the trees were there), the behavior of the cars were fine, even through many renders.
Changing the ‘count’ works, but places different cars in the trees. Changing Seed, Tension or lateral also has no effect.
[UPDATE: Found it… Maybe??]
I did have another issue with trying to place cars with the Spacing tool on a sloped surface (i.e. Garage Ramp) - the orientation of the cars did NOT want to cooperate or work properly. I gave up on the tool and ended up placing each car individually, rotating and moving into place. A pain, but it worked better.
Cars In Trees:
Original (Cars on Street):
COLLISION settings for Model Elements:
Spacing settings:
After changing Collison, select a new Seed & hit Update.
Hope this helps!