Realtime reflection probe limit

Is there a known limit to the amount of realtime reflection probes that you can have in a scene?

I switched all of mine from baked to realtime to do some realtime GI testing and all my shadows disappear. After some messing around I discovered that this only happens when I have more than 29 realtime probes at the same time. Is this normal?

 

My best bet would be that using so much real-time reflection probes eats up a lot of video memory.
If not enough video memory is available unity will disable shadows to save some VRAM.
On the other hand im not sure if its performance wive a good idea to have 29 real-time reflection probes running all the time.

 

Thanks fffMalzbier, That makes perfect sense.
I have been getting great results with baked GI and baked reflection probes but recently I added a lot of Speedtree assets to the scene and the LOD's seem to wreak havoc with the lightmaps. Haven't been able to get a single bake to complete since so thought I would give the realtime workflow a shot. I guess ill go back to trying to get the assets to work in a baked workflow - cheers!