LR always starts with wrong Catalog

For years I’m using a LR Catalog located somewhere under c:\MyLightroomCatalog … since an update or so, LR now always starts with an empty catalog from C:\Users … despite I load the correct catalog - close LR - start again and it opens the empty one from its default location.

How can I fix this bug and force LR always to open the correct / only one / last one catalog like the decades before?