This is a sign of a fault with the seat switch
If the engine dies when you turn the blades on ( or the blades won't turn on ) confirms a fault with the seat switch ( or the wiring between it & the mower )
and can be the seat switch connector not fully plugged in or the two pole shorting strip is damaged on that Delta 6444-82 switch with the Delta 96549-OL connector.
This is what the two pole shorting strip looks like.
Just to finish up this thread. I removed the switch under the seat and secured the button down with zip ties and now all is well. Thanks for the advise.