General travel-times are off

Saterday I send 4 normal generals to an adventure at the same time. Somehow 3 of them still 10 minutes away when the first normal general arrived.

And this afternoon I send 4 normal + 1 fast one to an adventure at the same time. The fast one arrives, dropped of troops and then I send him back for more.
While he was already back home (2* 15 minute + some time on the adventure-island) the normal generals were still 4 minutes away.

It's not a problem that the generals take a few minutes longer. But something is clearly wrong.

This issue is already being discussed in this thread