Ive experienced the same issue
Any List that is downloaded to the phone (whist connected to Wifi (or mobile/cellular networks)) for offline use, will cause the app to crash when not connected to a wifi network.
This is particularly annoying as Im often caching where there is no mobile signal, and now I cant use Offline Lists
Ive tried clearing the cache, clearing the Geocaching apps data, uninstalling and reinstalling the Geocaching App, wiping the entire mobile phone - none of these have made a difference.
(Geocaching App v7.6.0, Android 6.0.1 on a Samsung Galaxy S5 Mini, and this also happens on a Samsung Galaxy S7 running Android 8)
If anyone has a solution to this I would be grateful to hear from them - please message me at weredunn4 on the Geocaching Messenger app.