I've recently started seeing what appears to be random, extremely large values for my Explorer return times and my production rooms.
For example: I have four explorers returning. None were out longer than a day. The time to return for all of them is in excess of 69260 hours. Oddly enough all four values are between 69262 h and 69271 h.
LIkewise my radio room (with two high charisma dwellers assigned) is now showing a projected completion time of 138520h 51m.
Nexus 7 Tablet
Android Version 5.1.1
Game auto-updated from store