fyi this 4-way problem was resolved after replacing the 3-way dumb lighted switch (as suspected) with a spare DV-603P. I intend to replace the dumbs with add on switches next.
main finding and my own conclusion - Inovelli switches don’t play well with dumb switches lighted or not. Best to use add on switches.
Its good you have your installation working. Its not clear how replacing a 3-way lighted with a dimmer would be a good combination.
I currently have a working 4-way with dumb switches where I will be changing to aux switches. This change is to get the added functionality of controlling dimming from the aux locations.
John
I just had the spare to try for now and it worked - I plan on replacing it with Aux switches soon. Thank you for the help!