Based on my work experience with the current company i am with, i have worked with both Quality engineers and R&D engineers/scientists. The common problem i have seen is that projects in fact due get delayed because of check ups and reviews. From what i learned is that in order to avoid having any issue with the Quality department, its best to ensure they are provided with all proper documentation and also to establish a proper protocol that way both departments are on the same page and aware on what each needs to follow to avoid inconsistencies. Many of the times i noticed that causes the most problems are when QA question a certain criteria and the proper documentation is not issued or could not be found, it’s their job to verify that this was set into place. Its a collaborative effort, at the end of the day they are working for the same purpose.