Ringtone keeps changing back to the original default tone (over the horizon)

[Members_NmfiOtj]

i have installed a mp3 file on the phone and moved it to the ringtone folder (internal)  and it works for a day or so then it reverts back original default tone. 

I have done the fowlling:

-Reset the phone (no help at all, I have even tried it on a formated phone(s20 5G)the same issue)

-Change back from darkmode to daymode (some forums say ti would work)

-moved the file to SD-card  and back 

any thoughts? 

[BandOfBrothers]

I wonder if the file is in some way not compatible,  corrupted etc.

If you change ringtone to another pre downloaded option does that stay chosen?

I use zedge.com which has tones in the correct file format and have worked fine for me.

It's a free service.

Perhaps give it a try and see what happens @Members_NmfiOtj