SSMS crashes when try to modify database diagram (v18.2)
On July 22, 2020 MS released SSMS version 18.6 and one of the items in its Bug Fixes list is Database Diagrams:
Fixed long outstanding issue with Database Diagrams, causing both the corruption of existing diagrams and SSMS to crash. If you created or saved a diagram using SSMS 18.0 through 18.5.1, and that diagram includes a Text Annotation, you won't be able to open that diagram in any version of SSMS. With this fix, SSMS 18.6 can open and save a diagram created by SSMS 17.9.1 and prior. SSMS 17.9.1 and previous releases can also open the diagram after being saved by SSMS 18.6. See SQL Server user feedback.
They refer to the UserVoice item that I mentioned below in my original answer.
That item got 1239 votes and is now marked as Completed and has a link to blog post by Drew Skwiers-Koballa, Program Manager, SQL Server. The blog post has almost identical text:
The 18.6 release is the second major release of SSMS in 2020 and packs several high impact changes, including a fix for crashes in database diagrams.
If you created or saved a diagram using SSMS 18.0 through 18.5.1, and that diagram includes a Text Annotation, you won’t be able to open that diagram in any version of SSMS. With this fix, SSMS 18.6 can open and save a diagram created by SSMS 17.9.1 and prior as well as by other SSMS 18.6 instances. SSMS 17.9.1 and prior versions will also be able to open the diagram after being saved by SSMS 18.6.
Here is my original answer that I wrote before SSMS 18.6 was released.
MS acknowledged that there is a problem with Database Diagrams feature in the SSMS as of 18.2 (Still 18.5.1). You can use the previous SSMS version 17.9.1, which supports all features of SQL Server 2017 that you use.
In fact, they removed Database Diagrams feature in SSMS 18.0, then returned it back in 18.1 after people asked for it, but it has a problem.
In Release notes for SQL Server Management Studio (SSMS) under Known issues (18.2) there is an item:
Database Diagram created from on an SSMS running on machine A cannot be modified from machine B (it would crash SSMS). See UserVoice for more details.
Vote for a fix on UserVoice: SSMS 18.1 Crashes when Opening a Database Diagram
The MS Product Manager replied there:
I’d like to provide an update on this issue/
Unfortunately, it is proving to be pretty complex to deal with this this ancient technology that is used by SSMS. That’s why it’s being quite challenging for me to find a fix.
I’ll keep working on this, but sadly there is no fix in sight yet.
-Matteo
Issue has been fixed in 18.6, updated it today and works like a charm, but mind that you have to recreate all the diagrams that you have created in versions 18.0 to 18.5. If you create them again with 18.6 they open without crashing.