VLAN - TCP blocked?

[GreenMatter]

I use latest version of OPNsense 23.7.10_1
Recently I've discovered that in one of my vlans opnsense interface can't communicate with couple of hosts using TCP (ICMP works). It used to be working and I don't see any firewall rules blocking TCP communication.
Those blocked hosts are hosts which are proxied by nginx (SSL termination); could it have something related to this issue?
How to troubleshoot it?