Problems Setting up External Connection to Home Assistant

I’m trying to expose my Hassio outside my local network. I think I’ve set everything up correctly, but I’m hitting some issues.

I’ve got a dynamic IP address that changes aggressively often, so I’ve set up a DuckDNS which refreshes every minute. It didn’t want to work at first, but getting the DuckDNS add-on in HA seems to have fixed that.

I’m using a Mikrotik router with two NAT rules set up. I’ve got a masquerade rule for accessing WAN from LAN:

chain: srcnat,
dst-address: 192.168..88.214 (the HA device),
out-interface: bridge,
action: masquerade

and a dst-nat port forwarding rule:

chain: dstnat,
protocol: tcp,
dst-port: 8123,
action: dst-nat,
to-ports: 8123

Accessing HA from the local network works perfectly, however outside connection is a hit or miss. Sometimes it connects without issues, sometimes it fails completely. I’ve also noticed that port checkers sometimes report that port 8123 is closed. I’m starting to think that my ISP is doing something to block the connection, but I want to be sure I’ve covered everything on my side before I take things up with them.

Any suggestions on what I can try to make it work?