I am using the "Copy Field Value To Linked Issues" post function to copy the FixVersion/s between issues of different projects. Although the shown version name is correct in the target issue, the copied version is "invalid" and cannot be further used.
The reason seems to be that the function is copying the internal version ID, but has to use the version name instead (at least when copy is done to a different project).
PS: Of course this requires that the version name is equal in source and target project. To avoid manual version sync between source and target project it would be much appreciated if as an option the plugin could create non-existing versions on the target project.