My paper is in R&R but I have concerns about the data quality. What should I do?
Talk to your co-author(s) openly about your concerns and ask for clarifications.
If such a direct confrontation seems uncomfortable to you, ask them to make the data openly available for anyone to replicate, e.g. at Zenodo, by referring to your university's internal regulations (I am sure there are guidelines about research transparency at your university). This should pressure them to ensure that the data are sound.
In addition, insist on making each co-author's contribution transparent in the form of CRediT (Contributor Roles Taxonomy). With this taxonomy, it will be public that you were not the one who handled the dataset, in case doubts should arise.