I'd like some help in listing the reasons why planes may not take off from a runway, which leads to clogging on the runway. I've experimented with 1-, 3- and 4- nodes on the runway, marked as such. If I understand it, the 1- or 4-node methods work, the 3-node method doesn't usually work. I've also read that some have found that 3- or 4-nodes may be placed on the runway, but only the last node (end of turn onto runway) is marked as "on runway". However, I believe I read that logic may be added to Flightgear Airports to require all the nodes be marked as "on runway" (true?). Note: I don't understand yet how FG Airports knows where the runway is.
Sometimes it seems a pushback made incorrectly (less than 90-100 degree angle between segments) can cause planes not to take off.
Are these basic principles correct? What are other reasons planes may get stuck on the runway and not take off, clogging the runway?