Hello Sandy,
If you go to Epson.com and search for: EcoTank Ink Maintenance Box T04D100 you can order a new one for about $10 + shipping.
The replacement is very simple, a cover with one screw, the old one slides out and the new one slides in and replace the cover.
You can find a YouTube video that shows the replacement, just search for ET-4760 on YouTube
I’m retired and haven’t worked on the Epson EcoTanks so I’d suggest you keep looking for a solution to the magenta intermittent problem. I’d guess magenta jet is getting clogged up or the electrical connection to that color is intemittently faulty. Keep searching, there is an answer