Idles fine for a while then it drops down to about 850rpm for a few seconds then back up, easy fix? It’s the later type engine without the crank problem
Sounds like it needs its idle reset have a look in the technical section as to how to do but 850 is high for a warm idle, so if its higher than that it sounds wrong.
As for the crank problem, they all have it, just different failure rates/time to get there.