Let's start with the conclusion. This is a bug with the Samsung firmware which was solved with the update in Feb 2024.
Setup:
Samsung Galaxy S20, S21, S22 series. Physical SIM (pSim) and eSIM. It doesn't affect every single phone of a model.
When the pSIM is taken out none of these problems happen with the eSIM.
The pSim by itself also worked without problems.
Symptoms:
1.Cannot receive calls on esim at times. Caller gets message that phone is turned off.
Samsung blames this on the network. That only the esim network randomly doesn't respond to the phone.
In reality the call is stuck in the phone queue.
Calling out from the esim fixes this problem for a while.
Taking out the pSim fixes this.
Sometimes when you take any of these two solutions, you all suddenly get the call ringing even though the original call was made half an hour ago. You cannot pick up this call and if you leave it ringing it will keep going for 5 minutes even the normally a call goes to voicemail in 30 seconds.
2. Cannot receive text msg on esim at times.
Sometimes they are delayed by 10 to 20 minutes. Other times they do not come in at all.
Again Samsung blames this on the network.
Calling out from the esim or taking out the pSim triggers any stuck messages to arrive right away.
I'm not sure how the network knows that I'm taking out the pSim as it's on a different network from the esim. More likely the text message is stuck in the phone queue somewhere.
3.Calls are slow to ring. This is when you have done one of the fixes above so you can actually receive calls.
When you call the pSim the dialler rings for 1s before the phone rings.
On the esim the dialler rings for 5-7s before the phone rings.
Again something is getting stuck somewhere in the phone. If you take the pSim out then it responds within 1s.
Troubleshooting
Upon notifying Samsung they asked me to do the following troubleshooting steps.
* Check if the device is turned on
* Check if the device has enough battery level
1. Check if the SIM card was previously inserted on an iOS device.
2. Check if there's a network outage in the area.
3. Check if their device has a signal.
4. Are you on a prepaid or postpaid plan?
5. Reset the APN (Access Point Name) settings to default.
6. Reset the device's network settings.
7. Boot the device into Safe mode and check if the issue will recur.
8. Isolate the issue by inserting another SIM card to the device, or inserting the SIM card to another device.
These are just stupid of course. The Full reset of network deletes all of your Wi-Fi settings etc which they did not warn about. It also destroys your connection with your smartwatch which you have to full reset.
Logs
They also advised to use the support in the members app to send system logs within 3 minutes of any of these issues happening. After creating every one of these scenarios and sending them logs for 2 weeks, they said they couldn't find anything.
With an had to modify the phone to setup silent logs. Something had to be running in the background while I was using the phone and then when an issue happened I had to run a special command to create these logs.
Again I created this for every scenario with the logs compressed into a file that was 100-500mb. I ran into the problem that the DropBox are gave me did not have space for a 500mb file. Perhaps I'm the first person in the world to create a silent log and they did not know how big it would get.
Eventually I did get the logs to them and then I had to follow up for another 2 weeks before I got an answer.
Alleged Solution
Eventually I got an answer. The text said that the phone sent an ack to the network multiple times which did not respond. Therefore it is a network problem and not a problem with the phone.
For this to be true that means the network decides not to respond when it says that I have the pSIM inserted and responds when I have it taken out. It also knows when I call out of the eSIM to quickly send all the things that it has held back.
I don't know how they try to explain the phantom calls 20 minutes after the real call.
Samsung offered that I could send my phone into them to check out. It would take a week also and they would wipe everything on the phone and they do not have any loaner phones for me to use in the meantime.
Real Solution
None of these excuses about the network made sense. It is clear that when the pSIM is inserted something is wrong with the firmware and it gets stuck in some sort of software loop or race condition. All the calls and text messages are stuck and sometimes they escape after a while.
The fact that you can either make an outgoing calls from the e-sim to break this loop or take the pSIM out is a clear indication it has nothing to do with the network. Trying to blame it on the network is poor form on the developers who obviously haven't even read my pages of reports.
The next day the firmware update for my phone came in. After this update everything was fixed and everything worked like my first dual SIM phone from 10 years ago.
So was it a software bug or did the firmware from Korea fix a network halfway across the world? You decide.
I really, really commend you on the effort and time you have put into this. Hopefully the update also fixed many of the other connectivity problemson these model phones.
My biggest worry is that they never understood why it broke and they don't know why it's fixed. Obviously the firmware would have been in development way before my reports. Hopefully it doesn't accidentally break in a future update and others can use this as a reference for testing.
With any problems, go to the Optus Shop! I always believe that to be the best option. They will know what happened with the Line. Sometimes they're able to help immediately if it's locally.. Personally I have never used 2 SIMs. I don't need that! It's asking for trouble! I have been with Optus for 11 years and had teething problems, as I call them. If ever you called the help line, they usually got to the problems. They might have to ask a couple of different people, but they got there!
The more they do to improve the phone,, the more problems we get! I only twice got a problem, once they let us know!
It's only now that I saw Korea while reading about the rules and regulations. Before another country came up! We never know!
