A colleague has a strange thing happening.

Before using mirror

After using mirror

This is what needs to be mirrored

And as long as not all entities get mirrored it's fine.

One can select a bunch on the left, a bunch on the right, or just a hand full of rows from the bottom or top but as soon as one selects the majority of it one gets the errors like shown and that for all entities.

Anyone seen this happen before ?