So I've got 2 Raspberry Pi 3s, one used for Rasplex and the other for Home Assistant. For both I've been chasing random issues for months - the Rasplex unit would have random issues with stuttering/buffering which I spent ages messing about with wifi and Plex server configs to resolve, figuring it was a network issue. Unit was running off a USB PSU rated at 3 amps so assumed it would have ample power. Similar story with the unit running Home Assistant - HA updates would usually fail after restart requiring SSH command line messing around to resolve.

Finally got around to dumping the host logs for both units and noted lots of 'Under voltage' detected errors, even though the PSU were well within the rated specs. Bit the bullet and purchased an official Raspberry Pi PSU for each - which are rated at 2.5A (so less than the 3A rated unit I was using). And voila - suddenly the Rasplex unit would stream smoothly 100% of the time and the HA unit updates ran perfectly every time with no more undervoltage errors in the logs. The number of hours that I sunk into trying to troubleshoot these issues far outweighed the $30 or so for each official PSU (and I see that the Pi 4 PSUs are even cheaper now).

So lesson learned - just buy the official PSUs and save yourself a heap of wasted time!