After updating from Material UI 4.2.0 to 4.9.10, I observed a change in behavior that seems to have originated in version 4.8.3.
When using a Select element with the multiple attribute, I noticed that the popup menu shifts after selecting the first item. In some cases, it moved multiple times as more items were selected, but in the provided example, it only moves when choosing the initial item. Here's a codesandbox showcasing this issue: https://codesandbox.io/s/recursing-morse-2omxy?fontsize=14&hidenavigation=1&theme=dark
I also included a code sample using Material UI 4.8.2 for comparison purposes. In this case, the menu remains anchored where it initially appeared even after selecting items: https://codesandbox.io/s/recursing-frost-pxlds?fontsize=14&hidenavigation=1&theme=dark
Personally, I prefer the behavior of the second example where the menu stays in place while I make selections. Despite exploring the API and trying different anchors, I haven't found a solution to prevent the menu from moving in versions 4.8.3 and above. Does anyone know how to achieve this stability with newer versions of Material UI?