I have a problem with the timers of the explorers. I have 2 explorers whose timers are 49564h when exploring and 24782h when returning

not a bug....returning is always half the exploring time

Has the time/date on your phone changed at all? that's generally why it would do that, you can set your date to 2017 go back into the shelter and they should appear back at the entrance, although this would be classed as cheating?

Lol, definitely sounds like you've been changing your phones date and time to speed things up.

I'm quite sure the game wasnt intended to be played like that, so I guess you have to wait 1032 days, or try and mess around with your phones date again.