What is the problem?
503 Errors while attempting to access 2nd printers' page
Unable to name USB ports.
Printers connection randomly timing out if left idle.
What did you already try to solve it?
Changed HAproxy settings to every solution known to google.
Changed second instance settings to every solution known to google.
Changing udev rules several times.
Adjusted long-running command time.
Additional information about your setup (OctoPrint version, OctoPi version, printer, firmware, octoprint.log, serial.log or output on terminal tab, ...)
OctoPi version 1.3.9
Raspberry Pi 3 B+
Creality Ender 3
iMaker STARTT
I don't have access to the logs at this moment, I will post them when I can, if required.