Emulator

Game Name?

All (though my testing was primarily SMG2, it seems to occur in all games)

Game ID? (right click the game in the game list, Properties, Info tab)

All (my testing was primarily SB4E01, it seems to occur in all games)

MD5 Hash? (right click the game in the game list, Properties, Verify tab, Verify Integrity button)

All (my testing was primarily fb32f9a81d099529e9400c7a3eaadb6c, it seems to occur in all games)

What's the problem? Describe what went wrong.

In recent versions of Dolphin (12902 and newer), the sensor polling using RealWiimote with DolphinBar appears to be broken.
Polling issues (my guess, not confirmed) cause weird stuttering on the pointer and make UI elements very difficult to click.
This is confirmed to not happen in older versions (12900 and older) and happens in all newer versions from 12902 onward. 12902 was also a RealWiimote change, which suggests that it was likely the cause.
I haven't tested with a real sensor bar, but my guess is it's something to do with input reading from the DolphinBar, not the sensors, as the DolphinBar does not behave differently due to being platform-agnostic.
Please check out the videos linked at the bottom of the post, which show the issue as well as a manual bisection.

What steps will reproduce the problem?

1. In an older version of Dolphin (12900 or older), load up any game with a Wiimote connected to a DolphinBar. The pointer should behave normally, with smooth input and no problems clicking any UI elements. I tested with SMG2, though any other game has the same issue.
2. In a newer version of Dolphin (12902 or newer, latest as of posting is 13268 which still has the issue), load up any game with the same circumstances as before. The pointer will behave somewhat erratically, with less smooth input, random jumpiness, and issues clicking UI elements.

Is the issue present in the latest stable version?

Yes (version 13268)

If the issue isn't present in the latest stable version, which is the first broken version? (You can find the first broken version by bisecting. Windows users can use the tool https://forums.dolphin-emu.org/Thread-green-notice-development-thread-unofficial-dolphin-bisection-tool-for-finding-broken-builds and anyone who is building Dolphin on their own can use git bisect.)

First broken version is 12902. 12900 and older work properly.

What are your PC specifications? (CPU, GPU, Operating System, more)

Intel i7-8086k
Zotac GTX 1070 Ti
32gb RAM
Windows 10

Is there anything else that can help developers narrow down the issue? (e.g. logs, screenshots,
configuration files, savefiles, savestates)

Here's a video of it working in an older version and not in a newer one: https://youtu.be/xpsjlcqOVmI
Here's a video of my entire bisection process to find the latest build that works, as well as showing the issues with UI elements at the end: https://youtu.be/Hy8erQDckpg
If you need anything else, let me know.