I got cunfuse for ppsspp android

[Tiantian]

I already use ppsspp for windows and it work just fine.
And when i try to use it on android, something happens and i don't know how what is the problem.

I use xiaomi note pro 7 (not rooted) 128gb
And i play arround 20-30 game which is a lot of iso's to store even for 128gb.

So i upgrade my storage by micro sd card 254gb to store all of the iso's

So here's the problem.
When i move all the iso to my external memory and i try to open it in ppsspp, the thumnail of the game that usually is a pic of the game and now it's just a grey background with question mark (pic attached),

i got panic to think all of the iso's were corrupt because i try to open the game and ppsspp just crash. And when i move 1 of the iso's back to my internal memory (on in game folder psp installed).

And i try to open it again on ppsspp it work like nothing happens, i thought maybe it's the formating problem for my external sd card.

And...... I kid you not, i move again like half of all my iso's to internal memory and the iso's were become playable again.

When i was about to format my sd card, i just quick check the folder external sd card through ppsspp file explorer and i see some of my iso that still in external memory become playable again (because the thumbnail back to normal) and i try it and it works like when i put it in my internal

And now i put like 15 of my iso's in internal and the rest like 16 or 17 in external

Because when i put another one to external the iso just gonna have questions mark thumnbail

That's the problem. Anybody know how this happens?
Because when i use the windows version

I put the ppsspp launcher in my external harddisk and the iso's in my download folder (like 30-32 of them) and it's playable