Question about TCP MSS option

I will really appreciate if you can give some advice about this issue.

This is a TCP conversation, the client announces an MSS = 1452, server announces an MSS = 1460, client uploads data to the server, this is a LAN environment, both devices are physically in the same Data Center in different VLANs.

The problem: A lot of TCP errors: retransmissions (> 3%), dupACK, out of order packets, etc.

What I see: , If I perform a tcpdump directly on client OS, I see a that client try to send a lot of packets larger than MSS, e.g. 3000 or 4000. Why client is building that's long segments ? could it be that TCP stack on the client side is not working as expected?

There is other TCP conversations between the same hosts but in the opposite direction, in that case, all packets are equal or less than MSS, TCP errors are minimal (<1%).

Thanks in advance.