Symptoms
Nissan's bulletins describe none. That is worth saying plainly rather than filling the gap: the documents set out who is covered and for how long, and refer only to "customer concerns including those expressed by customers in the class actions". They name no judder, no shudder, no failure mode. For how a CVT fails in general, see the CVT file — but nothing in that general description is a claim about your car, and Nissan has not made one.
Likely cause
Not stated by Nissan in any of the three bulletins. The class actions allege "a defective continuously variable transmission ('CVT') which can lead to poor transmission performance or failure" — an allegation, settled without a finding.
How should it be checked?
Work out which round the car falls in, then check the date it was first registered, because the clock runs from there and not from when you buy it. The extension covers "the CVT assembly and internal CVT components, gaskets, and seals, CVT control valve body, torque converter, cooler kit (if applicable) and reprogramming of the Transmission Control Module". Then ask whether the transmission has already been replaced under it — that is a good sign rather than a bad one, and the paperwork should exist.
How can you check it yourself?
Drive it from cold and from a genuine standstill, then hold a steady 40 mph and lift off and back on gently. A CVT should change engine speed smoothly and independently of road speed; what you are listening for is shudder that comes and goes, or a delay between throttle and response. Do it before the car is warm — a warmed-up CVT hides more.
The question to ask the shop
When was this car first registered, and has the CVT ever been replaced or the valve body repaired under Nissan's warranty extension? Has the transmission control module been reprogrammed? Is there a service record for CVT fluid, and at what interval?