Unable to change Discount Price on already discounted products

A client’s store is showing a weird bug where products that already have a discount cannot have their price changed (you can change it in the Admin interface, but those changes aren’t reflected in the shop). I assume the problem there is with the database, that an update that’s been done in the past f*cked something up with their data. But I don’t know much about the magento2 database, and of course documentation isn’t really there either. So, any pointers would be greatly appreciated.