Discord randomly kick out a single call on mobile

I have a huge problem... Maybe a bug, but just maybe...

I have a 13 yrs old son, and I usually work every day, but he sleep with me online while I'm on shift.
We using Discord together, and more often realizes that, Discord randomly shows he is kicked out the call middle of the night (3AM), and I have to wake him up, to rejoin. This happening now at least 4 months, or more, but not every day, because sometimes the call is still on, when I come back to check him.

He told me, when this happen, there I'm still in the call, and I call him while I'm in the call.

I cannot understand the problem, and however I try to fix it, can't work.

Somebody have a solution for this?

Ps.: We using Bucharest server, I'm on Android, he is on PC.