Got the issue with @StickerTagBot's inline queries not working sorted out.
The backup server was running an old version of the database runtime, and upgrading it to the latest version revealed that it was not able to allocate enough memory.
Adjusting the related kernel setting resolved that.
The backup server was running an old version of the database runtime, and upgrading it to the latest version revealed that it was not able to allocate enough memory.
Adjusting the related kernel setting resolved that.