Not sure if its going to be the same thing but I have built a DIY DTG using an EPSON R1900 and this error is due to the PW sensor in the print head not getting its reference reading correctly. Three ways to get around it, turn on the printer in a dimly lit room, put the original under carriage back in when turning on, or remove the PW sensor altogether.
It is a error to do with the pw sensor i have done a Epson r210 and have had the same issue i can fix it by putting the original black base plate back in on start up but is not ideal as you have to remove again before printing but does solve the problem. I have try black tape seemed to work first time now it won lol so no go with that yet also my red dtg base witch is a old bread board lol seemed to work once or twice but cant get to work all the time so im still back using the original black insert until i find a solution. Did you ever sort this out please let me know :)
Hello! I've built a dtg printer with Epson R300 and my problem with the PW sensor removing it does not fix, there is another possibility to disable it. Software, hiding a dark plastic ... thanks