Port 443 Blocked on IPv4

I'm using one of my home computers for file synchronization with my laptop over port 443.   It has stopped working whenever I use remote Wifi that has IPv6 disabled.  I checked using nmap, and it shows port 443 is filtered with no response on IPv4 only.  I've also used 3rd-party port scan sites to verify IPv6 is working and IPv4 is sometimes not working.  If I switch to an IPv6 connnection such as cell phone tether, or if I tunnel into the network and use IPv4 inside the tunnel, everything goes back to normal.

The 443 filtering has be intermittent.  It will work for a little while and then randomly lock me out after a while.

Since this is preventing 2-way traffic between my personal computers in some situations, I'd like to know if there's any solution other than VPN, so that I could also access files remotely when I need to use someone else's computer?