I'm posting this as I submitted a bunch of info to the issue tracker 6 months ago and it's still listed as simply 'confirmed'. The issue still exists, frantic googling has only returned scores of people with the same issue and nobody offering a fix. At this point I'm just desperate to have someone give more ideas for fixes to try.
When holding down Z and attempting to free rotate an object, the rotation bugs out constantly, snapping to random angles and jittering all over:
you can tell from the UI that angle snapping is off (a suggested cause of the problem), but this happens even if angle snapping is turned on:
Advanced rotate DOES work, and has made it tolerable, but sometimes it's easier to just quickly rotate something with Z+mouse than the hassle of using advanced move.
I did some more testing, using an accessibility option to highlight the location of the pointer, since planet zoo hides the cursor when you rotate.
(Mouse settings - Additional mouse options - Pointer Options - Show location of pointer when I press the CTRL key)
From this gif it seems like for some reason, occasionally, the mouse pointer snaps to the middle of the screen, and then back again. I'd guess it's this snapping that causes the rotation to jump all over, but if someone who doesn't have this bug could attempt to use the same accessibility setting (or some other way to show the mouse) and let me know if this happens to them, it would at least rule it out.
This is in line with another experiment, some people noted that rotation would work as normal IF the mouse/object was in the dead center of the screen. I'd assume that if the mouse is already in the middle of the screen, it jumping back and forth between the center and the intended mouse location makes no difference.
To further illustrate this, here are two attempts to rotate by moving the mouse slowly to the right. On the left, the object is in the center of the screen. On the right, it was off-center. Again, both of these are with the mouse being pushed to the right.
Here's a list of everything I've tried.
When holding down Z and attempting to free rotate an object, the rotation bugs out constantly, snapping to random angles and jittering all over:

you can tell from the UI that angle snapping is off (a suggested cause of the problem), but this happens even if angle snapping is turned on:

Advanced rotate DOES work, and has made it tolerable, but sometimes it's easier to just quickly rotate something with Z+mouse than the hassle of using advanced move.
I did some more testing, using an accessibility option to highlight the location of the pointer, since planet zoo hides the cursor when you rotate.
(Mouse settings - Additional mouse options - Pointer Options - Show location of pointer when I press the CTRL key)

From this gif it seems like for some reason, occasionally, the mouse pointer snaps to the middle of the screen, and then back again. I'd guess it's this snapping that causes the rotation to jump all over, but if someone who doesn't have this bug could attempt to use the same accessibility setting (or some other way to show the mouse) and let me know if this happens to them, it would at least rule it out.
This is in line with another experiment, some people noted that rotation would work as normal IF the mouse/object was in the dead center of the screen. I'd assume that if the mouse is already in the middle of the screen, it jumping back and forth between the center and the intended mouse location makes no difference.
To further illustrate this, here are two attempts to rotate by moving the mouse slowly to the right. On the left, the object is in the center of the screen. On the right, it was off-center. Again, both of these are with the mouse being pushed to the right.


Here's a list of everything I've tried.
- -legacymouse 1 option in steam settings didn't work
- Verifying game files didn't work
- Updating mouse drivers didn't work
- running Planet Zoo as an admin didn't work
- Changing the hotkey used didn't work
- Changing the camera settings didn't work
- Changing mouse sensitivity didn't work
- Disabling controller support via big picture mode didn't work (this PC has never had a controller attached to it)
- Uninstalling and reinstalling the entire game didn't work
- Changing the monitor planet zoo runs on didn't work, nor does using just a single monitor
- The issue is the same in fullscreen, borderless or windowed mode
- Disabling overlays such as steam, discord, f.lux and so on didn't work.
- Updating graphic drivers didn't work
- Unplugging and replugging the mouse didn't work, nor did using a different mouse, nor did using a wireless mouse, nor did plugging the mouse into a different USB socket.
- Switching to a different PC DID work. An older PC that struggles to run planet zoo nonetheless did not have this issue, even using the same mouse. You can see the basic specs of both my current and old PC here. Obviously as the old PC does not run planet zoo well at all, this is not a solution.