I just went through a similar problem, wanted to add the issue and solution I hit. The branch was made from a SUBFOLDER of trunk and not the entire tree. Thus, when I tried to reintegrate, I was mismatching hierarchies. Simply restructuring the integrate to be to the proper subfolder of my trunk WD allowed the process to proceed.
Adding in hopes this might aid someone who hits this Q/A. :)
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…