Read-confirmation non reliably received

DC 1.20.5
Android 10
Samsung S9
email-Provider GMX

I just use DC in one single chat with one person.
Transmission confirmation is reliable.

I don’t receive reliably a read-confirmation from the other side. Sometimes a read-confirmation arrives a day after my chatpartner had answered my message (indicating he had read it), Sometimes I never get it.
I checked the email-communication and know, that the corresponding confirmation email did not arrive at my place.

On the other side, I sometimes receive a double confirmation on one single message. It might be coupled with the situation, if a picture was included.

My communication partner uses the same email-provider and a DC 1.20.2 client.

Is it Android too, or Desktop/iOS?

also Android

To add on, the latest observation:
Again, on receiving an answer, I contemporaneously received all readconfirmations from all messages of the last 24hours in a bunch. Despite they had been read many hours before.

Tonight, confirmations came along with a reply of my chat partner. So that might have worked OK.
The point is: I do not reliably receive Read-confirmations after my chat partner read the message with DC on an Android phone… Sometimes they come quiet soon, some times they are delayed by some hours or a day,
I cannot recognize a systematic. Possibly there is some coupling with the time, when the chatpartner sends a message.

OK, there is no coupling between sending a read-confirmations and sending a message. Today, I receive read-confirmations shortly again, without a message.

So it is just unpredictable, there are phase, when confirmations are released at once and others when they are delayed by hours or a day.

So I have to state, we could not unwind the temporal unreliability of the ReadConfirmation, as right now it works fine.
Thank You for discussion and input
best regards