Update: I found a new bug under this category that might be connected, so I’ll just reply here:
If you select a slider and press “ctrl + z”/“cmd + z”(Without letting go of the selection), Roblox Studio would combine the undo steps together, and you’ll permanently loose 1 undo step: If you redo, it would redo them(The previous step) both together, even if you edited them separately.
Note: This happened with the “New studio UI” Beta feature enabled.