TCP, how to determine the causes of frequent retransmits in sessions?

Question

Computer networks

Good afternoon.
From some point, delays in the provision of services began to be observed.
For example, for a while, the application's client interface freezes, does not respond to user actions, then it works fine for some time, and so on. Failures in work are observed only in the evening and on weekends. Comparing the dumps during normal operation and in the evenings, I found a large number of TCP Retransmission and TCP Dup ACK. As far as I understand, the reason for the unstable work is this.
How to find out the cause of retransmits?

Answer 1

To begin with, it would be nice to know what kind of network (LAN, or Internet) is made on what equipment.
In addition, symptoms such as "the client interface of the application freezes, does not respond to user actions" are more like a problem with the disk or processor load than the network.

Answer 2

Or drops, or one of the hosts freezes with the transfer. And that, and that is well visible in dumps.