question

As you mention, the AGV type (as well as the load type) is only evaluated when starting a travel task. So in order to update the type during the travel you have to (re-)start the travel. Either by stopping and resuming the task executer or by creating a new preempting task sequence.

The attached model uses waypoints in front of the "crabbing path". By looking that the upcoming allocations in the agv node, the logic determines if the AGV is about to switch lanes. If so, it switches the type and creates a preempting task sequence, sending the AGV to the path entry, exit and a further "crabbing end" control point. (The three separate travel tasks allow the AGV to come to a stop before continuing onto the crabbing path.)

The "crabbing end" point is a further waypoint that resets the type. Since the AGV will resume its previous tasks sequence upon arrival at that point, the type will reevaluated and the AGV will turn at the next corner.

crabbing-agv-fm.fsm

If you intend to use the crabbing path in both directions, you should place a control area around it to precent deadlocks.

Edit: Here is a version that adds messages to the task sequence. In the task executers' On Message triggers the shape factors are adjusted so they appear to travel sideways on the crabbing path.

crabbing-agv-fm2.fsm