Unable to open PBIP File - ConnectionString is not in the expected format

[Mario_Lehmann]

Hello everyone,

we get an error since one of the last power bi updates. When we open any of our existing Power BI Project File (.pbip) with PBI Desktop and simply save them with or without changing content then we get the following error message when we reopen that saved file.

Error Message:
An error occurred while trying to open [OurFilePath]. ConnectionString is not in the expected format.

We connect to a power bi service semantic model which has a live connection to a OnPrem SSAS Tabular Model via Gateway.

We saved our files in Git, so we see that the definition.pbir file has been changed by saving the .pbip file with PBI Desktop. There are two suspicious changes:
1) The Connections String Syntax changed from:

"connectionString": "Data Source=[OurSSASServerName];Initial Catalog=[OurDatabaseName];Cube=Model;Integrated Security=ClaimsToken",
"pbiServiceModelId": [OurModelId],

to

"connectionString": "Data Source=powerbi://api.powerbi.com/v1.0/myorg/[OurWorkspaceName];Initial Catalog=[OurSemanticModelName´]";Cube=Model;Access Mode=readonly",
"pbiServiceModelId": null,

2) The connectionType Property changed 

from: "connectionType": "pbiserviceOnPremLive"

to: "connectionType": "pbiServiceXmlaStyleLive"

If we just reset the definition file via git, we can reopen the file without any problems, so we have a workaroud for this problem. But I don't think this behavior is correct or intended.

Can anybody help us with this problem?
Thanks!

PS: Original Post here: https://community.fabric.microsoft.com/t5/Developer/Unable-to-open-PBIP-File-ConnectionString-is-not...