As mentioned above, to check for likelihood of future case separation, look for a shiny ring around the case near the case web, second, use a sharp tipped hook type test probe inserted into the case head. If you can feel a groove with the probe inside the case (harbor freight has cheap sets) around the shiny part, that is a case that will probably separate in the future. Another way is to use the old Stony Point (now Hornady) case headspace set. With calipers, it measures your ammo before and after and gives you pretty precise headspace in rimless cartridges. If the case requires excessive resizing then it will probably fail in short order because brass is too stretched to fit the chamber. Necksizing only is called for.

Re scratches, you can polish the chamber but it can make an already generous chamber more so. Scratches in chambers that are deep either require living with it or replacing the barrel for the original caliber.

It could also be a result of dirt or grit in the chamber and action especially if it does not occur on every case. That remedy is simple, run a cleaning patch before shooting and after and keep your ammo clean.