I hadn't done a 90 day report since before covid but was able to do online when we returned towards end of 2022. We also travel frequently between neighbouring countries but it wasn't a problem.
I remember having some trouble myself when trying on phone. I then tried on chrome on iPad and took off VPN and it went through. The confirmation of registration came into email inbox but the actual email for the report went into my spam.
At Jomtien office I was told because we are owners we don't have to report each time. That was a few years ago and never had a problem since, including online 90day reports and visa extensions.
in that case your 30days visa exempt followed by 30day extension from immigration office is your best option. It's not customs or immigration who query your length of stay but sometimes the airline at check-in, I've been asked about onward flights by a couple of middle eastern airlines in the past and also checking in in Vietnam. Their thinking is that if you're refused entry the onus is on them to fly you back
Easy solution is to get a 60day tourist visa from Thai Embassy in your country before departure, that way you're fully covered without having to go to any immigration for extensions
I'm not sure about the machines. We were travelling on an early flight to Vietnam last month and it was a total sh*t show. crazy queues and total disorganisation at Dom Mueang