Only Have One Unmanaged Solution
A pattern for safe development of microsoft-dataverse customisations.
When multiple unmanaged Dataverse Solutions exist within an instance, all change exists in the unmanaged layer.
The notion of being grouped into a solution only applies when the solution container that is used to logically group a set of unmanaged changes is exported.
There is no isolation between the unmanaged components and therefore it is easy for one or more components to be changed and included in more than one solution container. When deploying to downstream environments, change in application behavior may not be predictable because it will be based on the order of solution import or the layering order for solutions present in the system.
It is also possible to inadvertently create cyclic dependencies that prevent solutions importing.