Session Cannot connect to server

After upgrading software last two months, I have seen 3 sessions cannot connect to server. They worked before, nothing changed on our network, no AV or Firewall blocks ScreenConnect client software.

The session keeps trying to connect to server. It retries after 21 seconds. It tries for about 10 times. On our control website, I see the session is green then disconnected. I tried to reset the ScreenConnect service. The session keeps trying to connect to server again but cannot. I tried to reinstall the session, but it did not work. I tried to change IP address. It worked but it did not work after a few hours or days and then it did not work for the new IP address. I changed back to the previous IP address, and it worked. If I reboot the machine, the problem may come back. Our network does not block the IP address because the sessions on more than 30 machines on the same network work. We haven't changed anything on our machines and network.  

I think the issue has happened after I upgraded last a few months ago. Machines worked fine for years. ScreenConnect client on three machines cannot connect recently. 

Here is an event log:

System.Net.Sockets.SocketException (0x80004005): A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond
at System.Net.Sockets.Socket.Receive(Byte[] buffer, Int32 offset, Int32 size, SocketFlags socketFlags)
at ScreenConnect.SocketNetworkConnection.Receive(Byte[] buffer)
at ScreenConnect.NetworkConnection.<.ctor>b__0_0(BlockBufferReadStream stream)
at ScreenConnect.BlockBufferReadStream.OnNeedsBufferCycled()
at ScreenConnect.BlockBufferReadStream.Read(Byte[] buffer, Int32 offset, Int32 count)
at ScreenConnect.Extensions.ReadByteDefault(Stream stream)
at ScreenConnect.BlockBufferReadStream.ReadByte()
at System.IO.BinaryReader.ReadByte()
at ScreenConnect.MessageSerializer.Deserialize(BinaryReader reader, Type requireBaseClass)
at ScreenConnect.EndPointManager.ReceiveMessage(BinaryReader reader, Type requiredBaseMessageType)
at ScreenConnect.SocketEndPointManager.RunIncomingThread(ThreadSharedState threadSharedState)

Version: 22.8.9717.8313
Executable Path: C:\Program Files (x86)\ScreenConnect Client (98e0da85058f8df5)\ScreenConnect.ClientService.exe