You have covered over the problem by installing a bigger and more stable battery bank - which acts as a buffer to your converter.
You still have an issue, which could be one (or both) of 2 things:
- your converter output voltage is not what it should be - either too low, too high, or insufficiently filtered. In the not so long term, this will sap the life of your new batteries.
- your LED lights do not tolerate wide enough voltage swings because of poor driver circuits.
To determine what is really going on, you need to measure voltages and observe the lights running on battery alone (camper unplugged, you should see 12.1 to 12.7V depending on state of battery charge) and running on converter alone (plugged in, batteries disconnected. If it's a WFCO converter you should see 13.7 +/- 0.1V). Finally, plugged in with batteries connected you should see 13.7V, dropping to 13.2V after 2-3 days.
Improper voltages when plugged in are a bad converter. Flickering with good voltages are weak LED driver circuits.
hope this helps
2019 Flagstaff T21TBHW A-frame
2008 Hyundai Entourage minivan
camping Colorado and adjacent states one weekend at a time