With lamassu-machine v3.5.1, machine logs are now uploaded to your server and displayed in the admin's Logs panel.
However, these log entries by default are shown oldest first, thus eventually not displaying the latest log entries.
This is corrected in an upcoming server version, though for now, you may run these two commands in your server's terminal so that logs are shown newest first:
curl -#o /usr/lib/node_modules/lamassu-server/lib/logs.js https://raw.githubusercontent.com/lamassu/lamassu-server/7c7f2866fef7558676456243efe25357b576de15/lib/logs.js
supervisorctl restart lamassu-admin-server
Afterwards, please refresh your admin window and you'll see the latest log entries in the Logs panel.