After the massive amount of reshoots on Rogue One which actually changed many parts of the story arc in the one off Star Wars film, fans are wary of hearing the words 'reshoot'. However, it's all part of the filming process. Most major releases will undergo some level or amount of reshoots during the production phase of the filmmaking process. Things may need fixing or retooling and sometimes the shots they initially filmed don't work for some reason. Hence, reshoots.
With Rian Johnson completing most of the production back in the summer and John Williams currently hard at work on the next Star Wars score, they'll be heading back to Scotland and Ireland to polish up whatever they need to complete the film. Whether or not this may have to do with the untimely death of Carrie Fisher remains to be seen.