I'm on 19.1.6 and was just adding an alt-name to one of my LE certificates and it seems that HAProxy won't properly restart - I've let the LE plugin perform it and I have tried it myself manually through the general diagnostics page. I have to reboot the entire firewall to get any new web connections to complete. I see the following logged:
configd[89577]: Timeout (120) executing : haproxy restart
As far as the dashboard is concerned the service is till running.