Donaldson-Thomas invariants and flops

This is an erratum for [6] (which essentially coincides with [4]). The main result [6, Corollary 3.27] is correct. Indeed, if one assumes throughout to be working in [6, Situation 3.24] (namely, if only cares about flops) then the whole paper is fine as is. However, the key [6, Theorem 3.23] is incorrect as stated in its full generality. To reflect this, the arXiv version of the paper has been updated to [5]. This erratum is divided in three sections. The first provides an explanation as to why some statements in [6] need to be modified. The second goes through the differences between [6] and [5]. The third is an appendix to [6], which is parallel to [5, Section 4].