Previously, if you pressed Alt-L anything you clicked would be locked, and this is still the case. However; if you then pressed Alt-L again, the lock tool previously would have been deselected and you were able to continue clicking at your leisure.
Now, pressing Alt-L when the lock tool is already enabled does nothing and you have to select another tool (Select, Move, Scale, Rotate etc) to deselect the lock tool.
Clicking the lock tool in the menu also doesn’t deselect the tool.
I’m running the latest ROBLOX Studio version on Windows 10 and I noticed this bug for the first time today.