We have found Collector is fine (on-line and on-device) on Samsung and Apple. But only works on-line on Pixel 2XL and HTC. When you try to attach a base map to take a map off-line on Pixel 2 (and HTC) it crashes. Anyone have a fix for this?
Sounds like a problem with your specific map and / or device - I have a Pixel 2 XL and Collector works in offline mode. Logging a support case would probably be the best way forward.