EDIT: By any chance you wouldn't be in a multi-user environment (because in this case there may be restrictions depending on the actors). This would imply that this area is only accessible to certain people. See the data-manager in this case because someone could have made a modification concomitantly with the windows update
There are two of us, and we have the same problem. I got the Windows update a week ago, and since then I've had the bug. Yesterday my colleague had the update, and this morning, same problem.
These are new parts, and standard parts outside of toolbox or other.
I have the same problem, no more description, one of the solutions is to record under the part when you are in the assembly or in the drawing to prevent the description from disappearing but it's not very practical. I'm on windows 10 and I noticed that on windows 7, there is no problem (see image below). I'm on SolidWorks 2017 SP5.0 not possible for me to switch to 2018 SP3.