Why are delta bots so finicky?
user77232's points are valid but I have done several things to mitigate these issues on my Anycubic Deltas. 

First, both of my deltas have linear slide bearings. If your's has the bearing trucks that run in the extrusion slots this will lead to less precise operation and also is a source of wear over time. 

Second, be sure that the end stop micro switches are positioned precisely and that their fasteners are tight. You may also want to use a mild strength Loctite on their fasteners. When operated at high extrusion rates all components are subject to significant vibration.

Third, I found that the universal joints are also a significant source of play. I remedied this to some degree by placing rubber bands across the arms at both ends so that the play was minimized. The rubber bands should be wrapped fairly tightly to perform this function. 

Forth, I try to tune the belt tension so that all of the belts have the same note when plucked. There are smart phone apps that will help do this. I believe that one that I use is from Gates, a premium manufacturer of drive belts. Also, over time belts stretch so you will need to retension them periodically.

Fifth, run through the firmware calibration process regularly for both positional accuracy and for filament extrusion and retraction variables.

I don't use my deltas much any more since purchasing a popular XYZ type printer but it cost me three times what they did and it still has issues from time to time.