I have 500 PCs that connect to MySql server. The most of them work fine except one group of approx 30 PC with weird behavior. They sometimes can connect to MySql a sometimes not.
I use .NET 8.0 app and MySqlConnector.

dbConnection = new MySqlConnector.MySqlConnection(conString);
dbConnection.Open(); // exception here

Both good and wrong captures are same up to ACK packet. You can see 10 sec delay in wrong attempt after ACK packet No. 249. I dont know what client waiting for because in good attempt there is no such delay after ACK packet No. 650 and client immediately send another packet.

Wrong attempt capture:

Wrong attempt log:

Good attempt capture:

Good attempt log:

All group of these PCs are behind one router but i dont know if this router can cause some problem because according to captures it looks that client causes delay