@opera39x Hey, my first post here and I got here searching on the same problem. You've done a good job for not being a native English speaker. But let me see if I can restate the issue, it's buggin' the hell out of me.
Version 53.0.2569.141117 on Android v8.0.0 with the June 1, 2019 security patch all running on an LG VS996 (v30).
I listen to a lot of podcasts that I save locally as .mp3s. Up until ~around~ the v53 update I could always go back to the "Downloads" and pull up something listed there until I cleared them myself. Now, when I exit Opera and restart it that listing is blank save a watermark type image saying "No downloads". The thing not mentioned, in my case, is when I go to the folder listing they're all there (and dupes from when I redownloaded something I already had).
I've tried creating a new folder, on /root, and set Opera to use that one but the listing is cleared on every exit. But again, the actual files aren't being deleted, they seem to be hidden to Opera. I have not tried reinstalling.
Also, I've checked any settings I could find in Opera that might say to clear anything and they're cleared (to NOT delete anything).
Thanks in advance for any suggestions.