The Windows 10 October 2018 update was released in, you guessed it October 2018. However, Microsoft released the update slowly to users, as the update contained many bugs which had to be addressed.
Microsoft did address most of the issues in Build 1809. However, they did not fix the bug in which the Action Center would momentarily appear on the left. This issue has been reported by many people around the internet.
When I open Action Center in Windows 10, it briefly appears on the left side of the screen and then disappears and reappears on the right where it belongs. On multiple PCs.
— Paul Thurrott (@thurrott) November 20, 2018
However, this issue is fixed on the Windows 10 19H1 insider preview update. But it seems that Microsoft is reluctant to port the bug fix to the Windows October 2018 Update. Windows Latest tested and confirmed that the bug is still present as of the Windows 10 Build 17763.316 update.
Reddit user u/jacktheblue confirmed that the bug still resides within the February 2019(Build 1809) version of Windows 10 October 2018 Update. For all those who are looking for a fix will be out of luck, as the bug fix is only available in the Insider builds.
“We fixed an issue where the Action Center might suddenly appear on the opposite side of the screen before appearing on the correct side,” (Windows 10 Insider Preview Build 18267 release notes). This is pretty disappointing from Microsoft as not everyone has access to the Insider Builds, and on top of that, it is a pretty annoying bug. It will be interesting to see if Microsoft manages to fix this issue in The Windows 10 October 2018 update.