ID 350378 - Some user projects containing shared layers take an unexpectedly long time to open

Problem summary
Some user projects containing shared layers take an unexpectedly long time to open

Customer reported version
4.0v4
Customer reported platform
windows 10

Steps to reproduce

1) Open the attached file - *broken.mra

Result: It will take an hour or two to for the project to open successfully

2) Open the attached file - *improved.mra

Result: The time it takes for the project to open drastically improves

Workaround
To workaround this issue in the affected archive, each of the shared layers should be converted to copied layer groups instead.

Reproduced by support
Mari 4.0v4 - CentOS 7, Windows 7
Mari 4.0v1 - CentOS 7, Windows 7

No further regression check.

Expected behaviour
Shared layers should not have a large impact on the loading time of the project.

Actual behaviour
The project, when containing shared layers, took considerably longer to open irregardless of operating system.