Custom alarm gone and cannot be set anymore

[thuizt]

Hello, last week my custom alarm tone suddenly disappeared.
The file is in a .amr format and can be played on the phone. (Nexus 6p)
Tried with .mp3 but cannot set that either.
I have no problem setting my custom (.amr) file as a ringtone.

Looks like the default clock / alarm application is not scanning the alarm folder anymore.

Any ideas ??

gr. Sebald