Wow! I've never had a field trip go that awry, but I have had sims get stuck trying to get on the bus and it lagging out on occasion. But usually all I have to do is reset the sims involved and it fixes it. I also run NRaas Overwatch, which automatically tries to fix routing issues to an extent, so that might be why.
Also, the field trip rewards are all in buydebug, so if you want to skip the buggy trips but get the items for your sims to display like they did go, you can always gift them to them that way after you get the popup telling them what trip they'd be going on.