Have been using Power BI for last 4-5 years but haven’t seen this kind of issue. Even I am opening after few months relationship tab flow doesn’t changes.
Only Scenario I can think is if you are using Live connection and someone do changes at Backend or may be clicking on refresh button in Relationship tab can sometime affect Data model.
Regarding your query there is no feature to lock Data Model as it expected by default.
There is a bug in oct 2021 release which is causing the model view to either vanish or loose the layout design. The bug is verified by microsoft and i believe a fix has already been released by a patch update. If you update download the latest desktop release then most likely the problem would have resolved.
Hi @JohnG, we’ve noticed that no response has been received from you since October 15.
We just want to check if you still need further help with this post? In case there won’t be any activity on it in the next few days, we’ll be tagging this post as Solved.