Any electronic/electrical components have lifespan. While some can be fixed by reinitialising or updates, some can't.
For your case, there are only 2 possible causes. 1) Software(Android), or 2)hardware(the connectors from the motherboard to the sdcard unit or the sdcard itself).
1) You can usually fix this by reinstalling your Android via PCC.
2) There's nothing you can do about the connectors issue but to bring back to Sony service centre. But if the problem is your sdcard instead, it might be fixable. The first thing you might want to do is to backup all your data while you can. Once done, reformat the SDCard. What this essentially does it that it will identify any bad/corrupted area and try to reformat the table structure so that those area won't be used. Most of the time this will fix the issue. But what can also happen is that more corrupted areas might be found during the process and this will eventually cause your SD Card to be unreadable.
So if you are very confident that the your SC Card is not (starting to be)corrupted, feel free ignore this whole post. If not, start backiing up your data while you still can. 😃
