Geometry Collection Bugs in 5.1?

Using 5.1 - I have a few geometry/rest collection problems which I feel like may be bugs -

These all crash and throw up the same error message, not sure how these are related to that array error though

I have a child BP with some Geometry Collection Components within it. A force field spawns next to them at begin play to blow them apart

  • If I try to set ‘simulate physics’ on any of the Geometry components at runtime it crashes immediately.

  • If I try to set a rest collection at runtime on any of them it crashes with the same error - Have tried removing the nodes and can confirm it is these two that are causing the crashes.

a slightly different problem as well -

  • If I begin play with no rest collections set in the GC components (empty) and set them at runtime, they are not affected by any force fields that spawn - but if I set the same rest collections before begin play (in editor) they are affected by force fields.

I also tried creating the GC components and setting the rest collections at runtime and have the same problem with no fields working

Anyone got any ideas or anything I can do here?