This happened to me with KP-51 and KP-52, didn't test with stock.

I have a 4 partition 32Gb SD card.

If I access as mass storage, write some files to the sd card, then eject the unit, then disconnect the phone. Sometimes the new files don't show when the card is remounted to the phone, until the phone is rebooted.

They don't show even if I remove and put again the sd card.

¿Anyone else with this issue?

Probably not related but I had a somehow similar problem once. The PC mounted the card as a big floppy and the phone as a disk with partitions. Or vice versa, don't remember which. Anyway, for a while the effect was the PC seeing one set of files and the phone another. Inevitably, after a while, the FAT on the FAT partition was overwritten and bang! Card unreadable. I ended up writing a simple program to rescue my data. Didn't trust automatic tools to do that for me

xvan, I notice the same problem and also I would like to know solution.

Well, at least I'm not crazy , I thought I was imaging things...
Is your SD partitioned?

Anyone knows where is the proper place to raise the bug?

connect phone to pc in usb storage mode with backupmenu , after that format microsd with gparted 100% fix

Manually unmounting and mounting again let me see de new files.
It's not ideal but still...