A large part of the problem is the RNC changed rule 16 in 2014 removing almost all of the rules preventing the delegates from voting for anybody other then who they were bound too.
https://ballotpedia.org/Rule_16_and_its_impact_on_the_2016_Republican_National_Convention
How is that a problem? I mean this time if they are bound, they are bound to Trump if primary went for Trump? Right?