I got another roomba at a pay-by-the-weight thrift store which made it $8
This one's a 690, they took out the zigbee radio that makes the lighthouses turn on automatically and put useless wifi in instead but there's nowt wrong with it, just wants a new battery
thing about roombas is, if you see one going begging, the filthier it is the more likely it is to actually work just fine
Like this thing had so much crap in its front wheel that it'd no longer turn, which is probably how it started throwing errors in the first place, hence ending up in goodwill, so 2 minutes of cleaning and it comes back to life and NOTHING is worn on this machine, the cogs in the brush head are bright white, the wheels are immaculate, it just failed because it wasn't taken care of and now with minimal effort it's back to working just fine
Now compare that to one of my roombas who've been dutifully maintained and cleaned until literally every part of them is 100% shagged out