Target iSCSI sometime drop connection

I'v got 2 Linux servers, Proxima and Lisa. Proxima is as iSCSI-target, Lisa as iSCSI-initiator connects to Proxima. An initial connection is successfully done. But while data transfering Proxima sometimes drops connection. **Proxima** \ Debian-11 +Proxmox, kernel 5.15.149-1-pve x86_64 \ iSCSI: targetcli-fb-2.1.53 \ IP: aaa.bbb.ccc.21 \ System Log:

07:36:26.079 kernel:: [6942463.448080] Unable to recover from DataOut timeout while in ERL=0, closing iSCSI connection for I_T Nexus iqn.2015-07.cz.domain.lisa:client,i,0x00023d010000,iqn.2024-07.cz.domain.proxima:backup,t,0x01
07:36:26.494 kernel: Unable to recover from DataOut timeout while in ERL=0, closing iSCSI connection for I_T Nexus iqn.2015-07.cz.domain.lisa:client,i,0x00023d010000,iqn.2024-07.cz.domain.proxima:backup,t,0x01

**Lisa** \ Debian-7, kernel 3.16.0-7-amd64 x86_64 \ iSCSI: open-iscsi-2.0.873 \ IP: aaa.bbb.ccc.20 \ System Log:

07:36:26.089 kernel:: connection1:0: detected conn error (1020)
07:36:27.167 iscsid: Kernel reported iSCSI connection 1:0 error (1020 - ISCSI_ERR_TCP_CONN_CLOSE: TCP connection closed) state (3)
07:36:29.167 iscsid: connection1:0 is operational after recovery (1 attempts)

**tcpdump**

:36:26.065241 IP aaa.bbb.ccc.20.36751 > aaa.bbb.ccc.21.3260: Flags [.], seq 120408213:120409661, ack 214825, win 7568, length 1448
07:36:26.065254 IP aaa.bbb.ccc.20.36751 > aaa.bbb.ccc.21.3260: Flags [.], seq 120409661:120411109, ack 214825, win 7568, length 1448
07:36:26.065266 IP aaa.bbb.ccc.20.36751 > aaa.bbb.ccc.21.3260: Flags [.], seq 120411109:120412557, ack 214825, win 7568, length 1448
07:36:26.065278 IP aaa.bbb.ccc.20.36751 > aaa.bbb.ccc.21.3260: Flags [.], seq 120412557:120414005, ack 214825, win 7568, length 1448
07:36:26.065290 IP aaa.bbb.ccc.20.36751 > aaa.bbb.ccc.21.3260: Flags [.], seq 120414005:120415453, ack 214825, win 7568, length 1448
07:36:26.065303 IP aaa.bbb.ccc.20.36751 > aaa.bbb.ccc.21.3260: Flags [.], seq 120415453:120416901, ack 214825, win 7568, length 1448
07:36:26.088573 IP aaa.bbb.ccc.21.3260 > aaa.bbb.ccc.20.36751: Flags [R.], seq 214825, ack 120416901, win 24570, length 0
07:36:28.592030 IP aaa.bbb.ccc.20.36752 > aaa.bbb.ccc.21.3260: Flags [S], seq 492965647, win 29200, options [mss 1460,sackOK,TS val 1736195842 ecr 0,nop,wscale 2], length 0
07:36:28.592053 IP aaa.bbb.ccc.21.3260 > aaa.bbb.ccc.20.36752: Flags [S.], seq 1204188907, ack 492965648, win 65160, options [mss 1460,sackOK,TS val 4010571466 ecr 1736195842,nop,wscale 7], length 0
07:36:28.592222 IP aaa.bbb.ccc.20.36752 > aaa.bbb.ccc.21.3260: Flags [.], ack 1, win 7300, length 0
07:36:28.842712 IP aaa.bbb.ccc.20.36752 > aaa.bbb.ccc.21.3260: Flags [P.], seq 1:49, ack 1, win 7300, length 48
07:36:28.842769 IP aaa.bbb.ccc.21.3260 > aaa.bbb.ccc.20.36752: Flags [.], ack 49, win 509, length 0
07:36:28.842713 IP aaa.bbb.ccc.20.36752 > aaa.bbb.ccc.21.3260: Flags [P.], seq 49:501, ack 1, win 7300, length 452

---------- ***Addition*** (accordance with comment by waltinator): \ Hardware of both servers seem Ok, all other services are without problem. \ The problem with iSCSI is from beginning. No hardware changes since then. \ Previously iSCSI connection was between server Lisa and server Zion (Debian-6). It was without errors. Server Zion was replaced by server Proxima (Debian-11). I believe the cause is a difference in the iSCSI software versions.