You're right I did face some issues too with this when one of the monitors was different but the solution was rather simple. Just had to add a Modeline in some file called 10-monitors.conf(1) and then it worked perfectly until I replaced the 4th monitor with the same configuration, then no such hack was required.

You're right it didn't work out of the box but it was very simple thing even though I'm relatively new to linux myself (relatively speaking)

(1) https://gist.github.com/r0xsh/4d1c7219ee63e4cee0c7fe1077559b...