I am using ArcGIS Pro 2.2.1. I am facing this problem since bit long with last couple of versions of ArcGIS Pro.
When I create a model in default tool box and save ArcGIS Pro with model displayed and subsequent ArcGIS Pro quit, on next ArcGIS Pro open with same project I get "Failed to open model" error message. After clicking OK, project open up and when click on model it also open up. Similarly, if I quit ArcGIS Pro after saving the project , with model close, on next ArcGIS Pro open after opening the project and trying to open model I get "Tool has failed to open" but on subsequent retry model opens up without any error message.
Not sure what is going on.
Has anybody observed this behavior of ArcGIS Pro displaying the error message but opening of the tool on second attempt.