"index was outside the bounds of the array" when opening query design

[SergioRTC]

Today I began getting the error message "index was outside the bounds of the array" when opening query designer in ssms v18.5 with SQL Server 2019 Express.

Any ideas?

Thanks in advance.

[#2]

@SergioRTC same here. Just randomly the Query Designer presents that error and only way of restoring it is by restarting SSMS. I'm using latest version. 

SQL Server Management Studio 15.0.18369.0
SQL Server Management Objects (SMO) 16.100.46041.41
Microsoft Analysis Services Client Tools 15.0.19342.0
Microsoft Data Access Components (MDAC) 10.0.19041.1
Microsoft MSXML 3.0 6.0 
Microsoft .NET Framework 4.0.30319.42000
Operating System 10.0.19042