enduser resets any connection to http port

[ilkondr]

just after flashing and first bootup (formatting FS done) captive portal doesn't work
any TCP connection to port 80 got reset

18:33:59.990401 IP (tos 0x10, ttl 64, id 59630, offset 0, flags [DF], proto TCP (6), length 60)
    192.168.4.2.33154 > 192.168.4.1.http: Flags [S], cksum 0x8982 (incorrect -> 0xbf16), seq 2229002487, win 64480, options [mss 1240,sackOK,TS val 689566673 ecr 0,nop,wscale 7], length 0
18:34:00.009169 IP (tos 0x0, ttl 255, id 1732, offset 0, flags [none], proto TCP (6), length 40)
    192.168.4.1.http > 192.168.4.2.33154: Flags [R.], cksum 0x2806 (correct), seq 0, ack 2229002488, win 5840, length 0

NodeMCU startup banner

NodeMCU 3.0.0.0 built on nodemcu-build.com provided by frightanic.com
branch: release
commit: f25dc56
release:
release DTS: 202112300746
SSL: false
build type: integer
LFS: 0x0 bytes total capacity
modules: crypto,enduser_setup,file,gpio,net,node,tmr,uart,wifi
build 2023-10-28 15:09 powered by Lua 5.1.4 on SDK 3.0.1-dev(fce080e)
cannot open init.lua:

Hardware

ESP-12F