I just wanted to share my experience with Collector crashing in iOS in case someone else is having this problem. Collector was crashing only on certain maps. I've have finally determined that the cause (for me anyway) is labeling. I was using a feature service with street name labels. I haven't found a workaround or solution to this problem yet other than just turning off the labels.#collector crashing
Thanks for posting this. I was having issues with Collector crashing in iOS as well, whenever I tried downloading a map at any resolution. I was initially using the Imagery Hybrid ESRI basemap (which contains labels). When I switched to the regular Imagery ESRI basemap, the problem resolved.