Didn´t have this issue on my first playthrough but it did come up on the second, the way I fixed it was fast travelling to the city center far away from panams mission then driving back to panam and entering the vehicle, worked after that no infinite loading. you didn´t get any replies but I leave my two cents here for anybody that needs help with this.

My guess is still the same since launch day. Much of the happenings are due to the heavy scripting. If you try and do something while (pick-your-script) is running, many not so good things can happen. This case may not be so related, but one never knows. The .8 second delay for letting you know a new item was received for 2.4 seconds. Then look, .8 seconds later, another item received and displayed for 2.4 seconds.

Things will back up behind them and stack. in the, what seems like, a FIFO queue.
Then drive around really fast, you get another stack, The Calling Queue. So many people all of a sudden know you (with no rise in Street Cred) and want your services.

Then save your game and reload. Any number of things happen on your load, including the queue restarting at the point of your save.