There appears to be a pattern emerging. Both P@t and juiceme formatted the card elsewhere. Curious.

If I undestood correctly, @karlos_devel can mount the card correctly when it is inserted to the USB socket but not when it is inserted to the SD socket.
(I assume it is put into some kind of adapter when inserted into USB socket, right?)

There is difference with USB and microSD, the adapter is not just a dummy piece with wires inside, it is a fullblown microcontroller that adapts the signals from one type of bus into another, handles timing, caching, access selection, etc...
Hence this only proves that the card works correctly.

Now, there are tons of reasons why it might not work in the microsd-slot.

• it might not connect electrically correctly (have you tried other cards? The same card with different filesystem, like exfat?)
• the filesystem might be somehow corrupted or aligned differently, in such way that the USB hostcontroller in the adapter recognizes it but the phone doesn't

Is the card recognized at all when it is in the slot? Do you get anything about mmcbl1 in dmesg or journal?

Yeah...about that contact thing. You might try cleaning the contacts. Simply take the card out and rub the contacts with a rubber eraser. I fixed quite a few PC cards that way back in the day.

No need for swipes, just press Power button once to powerup the phone, lift finger and place finger back to button again firmly (but not too hard to poweroff) and phone unlocks and is ready for use...

For me it works pretty much all the time perfectly, rare occasion needs to lift finger and place again for second "read". When I trained the fingerprint, I placed it in different angles, all around finger for good data.

At first I thought this method worked for me, then I noticed my phone wasn't locked anyway. When I put the code, using fingerprint tap doesn't bypass the lock code screen.
The fingerprint sensor only worked to the point where I put in 2 fingerprint profiles, after that no more unlocking, no more adding fingerprints.
Probably a hardware part that is intermittent?

About the unlock of Sailfish X by means of fingerprint:

Now I understand the behavior better.

First: to use fingerprint unlock you first have to apply a lock code to protect your phone before you can use the fingerprint feature (so it will always be possible to unlock by entering the code on the touch screen in case finger print sensor doesn't work)

Second, unlocking a locked phone: When presented with the lock code sceen it is possible to unlock the device by fingerpint scanner (double function of the power on / off button)

This seems to work with my device only if I patiently and slowly put my finger on the sensor and if nothing happens the first time (as is mostly the case) lift it and put it down on the sensor again, as widely covering the sensor as possible.

Impossible to use efficiently in stress situations and all weather circumstances I can imagine..

Also the placement of the fingerprint sensor of the Xperia X is not helping efficiency, especially when a case is used to protect the phone as the button is laying even deeper.

EDIT: immediately after practicing with unlocking by finger print, I went on trying to input another 3rd fingerprint. This doesn't work. After trial unlocking the phone by fingerprint doesn't work anymore but after the 10th or so time. A messag pops up above the code input: Locked, adjust your grip. I am holding it wrong

I have 4 fingerprints memorized on my Xperia X without issues, and even if I do sometimes have to try a couple of times before the fingerprint reading actually unlocks the phone ("adjust your grip", "fingerprint not recognized" etc.) I have now learned how to use it so that it unlocks the vast majority of times at the first try. I even have a pretty thick hard plastic case from Caseable on my phone. I guess I'm just lucky

There are 2 major problems with the fingerprint unlock that I see;

1.) I've got a plastic "skin" cover on my device which has a hole throuhg to access the power button. For some reason the case affects the finger just so that fingerprint scanning is very erratic. Without the case it works well enough.

2.) The more important thing is the fact that fingerprint is not a password, fingerprint is an user ID.
I'd be very confident using fingerprint in a multiuser environment to identify myself, but never in a million years to authenticate myself.

These two basic security concepts get confused all the time. No wonder people get hacked...

Iam not going to argue regarding terms @juiceme. But I feel more confident in using a fingerprint for identification/authorization than typing a PIN code. For the very reason that it prevents evesdropping when typing code.

Yes, there are solutions for that too, the random keyplacement lockscreen, picture lock, etc...

The problem of fingerprint is that it has been verified that one can create an "artifical finger" from gelatin and a fingermark left into glass or similar surface.