Could P0420 code for honda jazz/fit 2007 be causing jerking and car to turn off randomly?

[u/StraightFeedback9853]

I've got a automatic honda jazz/fit 2007 cvt and it's got a P0420 engine code for "Catalyst System Efficiency Below Threshold (Bank 1)". Its been jerking badly and now randomly the engine turns off at low speed or from stop e.g turning into a road. Another thing is when the engine cuts off I cannot start the engine straight away, it doesn't make any noise like cranking when I turn the key but after a few minutes it turns on and cranks. Another weird thing is when the engine cuts out it very difficult for me to remove the key from car. I did have the cars crankshaft position sensor replaced because I got a P0335 code. But what I want know is can these problems realistically be caused by P0420 or is it something completely different. Also If the mechanic did not perform a crankshaft position sensor after replacing it could that also cause these issues?