Hi! Sorry to hear you are having issues.
The LED array may still be good, but the LED Driver board may be failing. I have not personally seen a failure of the array yet on these machines, however I have noticed the same issues as you are having due to temperature in the room with the Phenom.
I turned the A/C off in the room and it started printing much better, I think the large format resin is slightly less forgiving to temperature as some of the other high detail small format resins, maybe something to due with additives in the resin itself.
Peopoly also sells vat heaters to keep the resin at a stable temperature over hours and hours of printing, as well as a enclosure heater to keep the build volume stable. These are upgrades that are available for the older machines and i have heard good things online about them. I haven’t tried them myself yet.
You could also run some exposure tests to try dialing in the setting a little better:
Chris