Car model/computational error caused when gear changes

Hi all,

I'm creating a model of a car with automatic gear changes when certain speeds are met, and is driven by a desired speed using the longitudinal driver block. This is done using a chart to output the gear with the car speed (vspd) feeding into the input.

For some reason when second gear is reached there is a spike increase in acceleration from ~2m/s2 to ~13*10^6m/s2 for a very brief amount of time. This causes a large increase in speed over a very small interval, therefore the car cycles through the gears extremely quickly. I can only imagine this is some kind of computational or solver error but can't find anything on the forums.

The model and required mat files are attached.

Thanks in advance!